"going to a big box store and purchasing a window is the same as going for a name brand window and having them install it."

Can you explain what you mean with this statement?

If you mean that the windows are the same at the big box store as you can get from a contractor, I think you're friend needs to do a little more research and you are right to question them. Windows have a lot of varying designs/levels and to believe they are all the same is plain wrong.

I think one of the big box stores sells a window that is a Simonton 5500 rebranded but this window isn't even shown at the store, it's only sold by their in home consults or so I have heard.

The way you've worded it, here is one difference: with the first option you'll have a big pile of windows in your basement, with the second option your windows will be installed in the frames!
But seriously, the windows from the box store WILL have brand names, so you need to find out what they are and compare apples to apples. Which box store? Which brand names? Sounds like you need to hire a contractor anyway, so get some quotes from contractors and ask them what brand they recommend. They will order direct from the factory or go to the box store themselves.
And ask your opinionated friend what she did last time she replaced her windows.

Thanks for the info. I would have never thought to ask where the contractor would get the windows from. I've had two window companies come and give me a bid - wow, pretty proud of the windows. I know a huge amount of the total cost is the install and warranty - I won't install them myself. What I'd like is to slowly - every other month or so - have a window replaced. Both companies said to do it in one install and be done. I figured I'd pay cash each time and be done - of course they offer credit, etc but when enough cash is saved then windows will be installed.

You very likely will have difficulty getting a company to install one window at a time. If you find someone who will do it that way, expect to pay a lot for the installation charge of each window. My guess is you will pay less overall getting them all installed at the same time with financing than doing it piecemeal.

Ask the companies how they do the install and what's included.
Ask them what brand of windows, model and features they are selling.
Ask them (if this concerns you) if the windows meet the 2009 Tax Credit requirements which is different than current energy star requirements.

Then if you have any questions come back with your finding and let the experts here give you their advice.

As to doing the job one at a time as another poster said that will probably be hard to do, you could buy the windows yourself and call someone to do the one once a month but for a company who lives off selling/installing windows they probably will want to do it once or twice. I have heard of companies doing half the windows at one time and then coming back later and doing the rest.

thx for all the great info - going to make some calls and will be back to report in on what I'm finding out