Ok i have just finished my system build and i have figured out that i want Windows 7 Home Premium x64. But i am confuses as to which type to buy.i currently have Windows 98 on disk. So i just want to know whether to buy OEM,Upgrade, 'Full' or something else that i don't know about.
OEM=Original Equipment Manufacturer, i.e. whoever built the system. You can find the price difference yourself. With a full copy, Microsoft will provide the Windows support, with an OEM copy, the manufacturer (in this case you) provides the Windows support.
Seeing as you built the computer, you are entitled to install an OEM copy.