you need to read about XP activations scheme ......... inputting the right XP sku serial will activate windows
But if you go on the web, it will try to connect to Msoft servers asking a genuine activation against your serial number, this is what we call WGA windows genuine activation
If the serial number was used too often you'll get an non genuine windows popup
Removewga kill this process, it does not generate serials, you still need a serial number according the XP sku IE: Pro, OEM, Family, VLK Sp2 Sp3 etc ...
There is a bios trick to automatically activate window XP Win 7 Win 8 ... SLIC but i wont venture there
i put a zip file earlier in my answer
its called removewga
Normally you install a windows version according to the serial sticker found on your equipment, if it say OEM, you need to have an XP OEM vesrion install disk
You have some google infos how to convert XP editions to suit your needs