Windows 7 needs a bit more of a hardware system that the average Windows XP hardware system.
Before you buy something you may not be able to operate properly do your homework.
For Windows 7 there is a program
Microsoft distributes (for free) called Windows 7 Upgrade Advisor.
You run it on your computer and it tells you if Windows 7 will function properly. It examines all the
hardware capabilities and gives you a report when it’s finished.
I have a personal opinion on the minimum RAM amount for Windows 7 and that is 2GB minimum.