According to the official windows memory limits, Win 7 only supports 4 GB of RAM. I, however have been reading some forums and some say they are using 8 GB RAM with good performance. I am wondering if I can use 8 GB before I purchase.
The system that allows an OS to use more than 4GB of RAM in 32bit machines is called PAE. Windows supports it, but according to Wikipedia the amount of RAM you can use is limited to 4GB anyway. (Maybe there is some hack allowing that limit to be removed?)
Read more about PAE on Windows: http://msdn.microsoft.com/en-us/library/aa366796(v=vs.85).aspx