go here and register for a license key. Then enter it in computer properties (My Computer > Properties at the bottom there is a link you can click to enter the key)
Of course this only applies to a legitimate version of Windows, not pirated ones. And it doesn't apply to the beta either, because that has expired.
My Computer
Computer Manufacturer/Model Number
Too many to list.
OS
XP, Seven, 2008R2
CPU
AMD, Intel, VIA
Motherboard
Various
Memory
Corsair, Kingston, etc.
Graphics Card(s)
ATI, NVIDIA
Monitor(s) Displays
Samsung
Hard Drives
Maxtor, Western Digital
Keyboard
qwerty
Internet Speed
22 Mb/s @ home, 1 Gb/s @ server
Other Info
All of my systems still run fastest on XP 32-bit for the most part. Win7 is fun to play with, but I still prefer XP for raw speed, security, and functionality.
We're a pretty tough crowd here, but you're new so I will cut you slack. If it is for testing only you dont need to activate it. You can use it up to 120 days legally. We dont condone anything illegal like hacking, cracking, circumventing activation, etc. In fact posting info abt that will get you banned.