All this advice is excellent and should be taken into account when choosing your windows and doors but the most important thing you should be looking into is INSTALLATION. You can have the most energy efficient doors and windows on the market and paid a small fortune for them but if not installed correctly then your choices (and money) were all for naught.
Shopping around for your contractor is just as important as shopping around for your installs. Never be afraid to ask questions even if they sound silly. Always ask for references, if he's good, he won't mind giving you at least 3. Also keep in mind, a contractor who is able to start work the very next day or within a 2 week period is someone I'd be leary of! With all the new construction going on out there (and reno work) you have to ask yourself the question Why is he not busy? What's wrong with his work? Also, putting a deposit down is a great idea, let's the contractor know you are definitely going through with this but the deposit should never exceed 10% of the estimate and you should always hang on to paying in full until the work is completed and YOU, not the contractor, are satisfied. Lastly but not least, never be afraid to ask for a written estimate and a written warranty/guarantee up front. Again if he's solid, he won't hesitate.

I changed all my windows from single glass alluminum panes to NAPA vinyl windows. I purchased them at HD. Depending if you want manintenance free or wood. With wood windows on the exterior expect to recoat them every 2-3 years. However, you can have vinyl on the outside and wood on the inside. Windows which are south facing should have UV sunlight protection. I have saved about $40 per month changing them to high effeciant windows. As far as one dealer to another, if it says energy wise on them then they are usually good because of government standards. It breaks down to where the best service is going to come from. I had a problem with one of my NAPA windows and the sales rep came from Kelowna just to see my problem.... Good Servce!

Working for a glass company in Ontario, I have to say that not all windows are created equal, so make sure to ask questions, questions, questions. Ask what type of spacer is used in the thermal unit: is it swiggle (garbage), super spacer, aluminum with silica beads, warm edge, etc. Always ask about the warranty, although 5 years is the industry standard for the glass. Low E and argon gas filled is the way to go, but it can get very pricy. Ask yourself, "How much sun does my house get?". If it is a fair bit, then go with the extras. They will pay for themselves. Whatever you do , though, DO NOT replace a few with Low E and argon, then replace the rest with regular thermal units. You will only be wasting your money. It's either all or nothing. Also ask about the frame itself: is it complete PVC vinyl, aluminum clad wood, or vinyl clad wood (personaly the best in my opinion, since it gives a maintenance free exterior, but a beautiful wood interior in most cases).
Again, just ask the questions before you buy. Just because a company has been around for years doesn't mean that you will get the best product, nor does it mean that the customer service will be there either. A lot of these companies are more wham-bam thank you for your money!

In addition to the previous 2 answers, and since you mention only some of your windows are having the problem, another possibility is that some thermal panes are leaking and allowing cold outside air to enter the sealed space. This too will cause excessive moisture or ice on the warm side of the inside pane. If the leak were allowing warmer house air to enter the sealed space, this causes fogging and moisture buildup between the panes. To test for this, try using clear plastic film specially made for outside use to seal the window on the outside of your house. Also try replacing the outside caulking around the window where glass meets the wood frame. If you do indeed have seal failures, this likely won't eliminate the moisture problem but may significantly reduce it until you can fully repair or replace the defective windows. Hope this helps.

In addition to the first answer, always make sure you run your bathroom fan and stove top fan when either area is in use. These are the two biggest sources of moist air inside your house, and since we keep our houses tightly sealed in the winter, the moist air has nowhere to go unless you vent.
Some guidelines suggest keeping the bath fan on for 15 minutes after using the shower. Many new homes have a fan control switch on the main level or near the front entrance to make this more convenient. Hope this helps.

Home Depot does NOT ever in any way cut down doors at the store level, they will however gladly order them sized for you if it is available witch yours should be.

The Home Depot supplier of French doors in Ottawa no longer uses the astragal that attaches to the edge of the door but a surface mount that attaches to the passive door. Consequently, the astragal does not add any width to the total unit. To calculate the width of the doors required for a double door unit, measure the inside dimension of the existing frame, subtract 1/8" for each door slab (-1/4 total) and divide the balance by 2 to get the door size. Doors can be ordered custom machined to size. Your local Home Depot can provide you with a sheet that shows the required information to ensure the hinges etc. are cut in the right place for your existing frames.
Your local Home Depot does not cut doors of any description.

In stock product, Yes two 36x80 doors are standard. However by special order, Milette will make you custom sized doors. Expect to pay extra.
As some of the other members said, Its easier to frame in your opening to accomodate a 72" door unit.
As for hinging. Standard would be side hinging for french doors.

Home depot sells stock in store french doors with mullions in the glass, they are made for replacement sliding glass doors as well as new applications, they are for a 72" x 80" opening, if you order them you can get them for a 74" x 82" opening, 80" wide is not possible and if you do find someone to do it it would be very expensive at very little benifit, better to make your hole 6" or 8" smaller and use a reguler size.

Home Depot sells 78' pre-hung doors

A few extra tips to add. When placing the spline in the grove start in a corner. When cutting the extra screen cut with the blade facing away from the widow to avoid damage. (Or you'll be replacing your screen again.) Finally make sure you're using the correct screen. There are many types to choose from including aluminium, fibreglass and pet-resistant nylon.

Sounds like you drilled the additional hole below the original one, instead of above. This has nothing to do with the brand or type of lock. I guess by now you have done a patch job on the door. I hope it turned out alright.

I have to agree with your take on doing the Tile first - make sure that you take the time to do it as per the manufactures instructions & complete the process through to sealing the grout.
The edge that will marry to your Laminate should be vertical & square so the when you butt the Laminate to it, it will be square.
Upon completing the Laminate instal - silicone seal between the edge of tile & the Laminate. Make the tube opening small and lay down a small bead of silicone, this will help keep the moisture out of the joint.

I am not sure but from Fort Erie you may be referring to a 'cellar" door which in 50 plus year old homes would be an outside access where the door lifted on a slant to access a stairwell to a cellar (low basement) often with a dirt floor and often referred to as a root cellar for storing and keeping vegetables. Still not sure how you know you require one if you don't know what it is so I may be off track here.

due to the changes in architecture and design, you can expect the door knob to be placed anywhere between 32-39", depending upon style of door knob.