I have read that vinyl windows are best for any weather condition since they can stand up to the elements. Is it true? If anyone has done replacing old aluminum windows, I would be grateful for knowing what brand of vinyl window is the best value in Ontario. What about this windows replacement windows replacement company? I heard about Home depot also. Any suggestions?

I have recently replaced all but one of my windows with vinyl ones. I went with two different companies. The one, from whom I got the majority, had been recommended by a friend who had used them for his rental property, had a better price.
The other replaced a window and also my front door. The second company has been around for quite a while and will likely still be here when the other has failed. I like that and sort of wish I'd just dealt with them.
It's a fickle business and it seems all the vinyl windows are quite comparable. Installation is the key.

Oh, I'm also in Ontario and the window makes were: Euro vinyl http://www.evw.ca/ and Home Tech http://www.hometechwindowsanddoors.com/.

I'd pass on having any box store or a place like Sear quote on the job.
None of them have has people on staff that install the windows, they hire the contractor of the week to do there work.
What to have some fun call them out for a quote, then call any local real window company or local licenced contractor.
Most often from what I have seen the box stores price will be almost double.

I had one broken double hung window replaced with a vinyl one. Despite what the estimator told me, it is not all vinyl; there's metal underneath one of the vertical strips, not that it bothers me.

I noticed a difference right away in the lack of air leakage and the warmth of the room.

Other than that, I have no experience with anything other than old leaky double hung windows which all need to be replaced.

When I was looking for a contractor, I did check the big box stores but was turned off by a manipulative policy to circumvent competition. I don't remember if it was Lowe's or Home Depot or both, but I was told that there was a charge for an estimate, which would be deducted from the cost of the job if they were the selected contractor. Otherwise, I was out-of-pocket for the estimate. I don't recall how much it was.

I do recall that I had also sought an estimate for installing fencing; the charge for an estimate for $30.

This is insulting; I would never consider one of the big box stores for installation of anything.