Google Craig, Google. If you don't already know the main features of Windows 7 you wont be interested in it. Many threads are on LOMCN about Windows 7 so if you haven't read them then go for XP. However;
If you want to run Windows 7 on your PC, here's what it takes:
•1 gigahertz (GHz) or faster 32-bit (x86) or 64-bit (x64) processor
•1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit)
•16 GB available hard disk space (32-bit) or 20 GB (64-bit)
•DirectX 9 graphics device with WDDM 1.0 or higher driver