Need PC advice

I am looking to get back to owning a PC. I have been a mac user for about the last 5 years and don't have anything to go with a pc anymore; no monitor, no windows, no office suite. So, I think I would be better off buying a pre-assembled pc instead of building one where I will have to buy a monitor and all of the software I will need as well.

I am trying to do this with the hopes of having a pc that I can upgrade at somepoint into a gaming rig, but no immediately. Immediate needs say that I replace the mac, which is dying a little each day. Budget is probably around $500. Also do the newegg pc's come with software already installed on them, like if I were to buy an iBUYPOWER rig would it have office installed?

Last question. Are there some programs that won't run on windows 7 64-bit ?

Thanks in advance for any replies.

This is a solid machine to get you going and Unlike most other prebuilts you can actually uprgade this one.

To answer your other question there are very few programs out there that won't run on 64bit this day in age

you want a monitor, OS and the tower itself for $500?? Impossible dude, unless you're okay with an xbox 360

So, another question. Cyberpower and iBUYPOWER are two companies that build pcs and you can upgrade anything on them, is emachines the same sort of company, and are there any other companies that build pcs that I can later upgrade?