My Hp laptop originally had xp professional loaded.This has been reloaded with xp home.Although I have the software key
I cant activate windows and every month it becomes inactive.I have heard that Hp also build in some sort of key?
Any ideas how I can prevent having to reload every month.

Tis correct. The big brands have a set of keys that work with their own xp install discs.

If you are trying to use the key that is stuck on the laptop it has to be for the actual product detailed. Ie you cant use a professional key for home. If it says on the sticker hp oem windows xp pro. Then you have to use a hp specific install cd for that product.(i have read of ways round the exact cd, but i have just got the right cd)

You don't need a HP specific CD to use the code on the bottom of the laptop. Any generic XP Pro OEM disk will work with that code. Big manufacturers do have a master code that they use, but it works in conjunction with a string embedded in the BIOS and a certificate embedded in the specific manufacturer CD.