Laptop with Spanish OS

I have bought on eBay a laptop; in really good nick; really cheap. Big problem is that the Operating System is in Spanish.

Does anybody know if it is possible to wipe the system and install an English OS

Yes it certainly is. Simply insert XP or Vista installation disc and choose to wipe the primary partition. You can most likely switch the language to English but I recommend you do a clean install since you don't know where this machine came from and it could be riddled with viruses and trojans.