My PC has XP Home SP2. I have an XP Pro cd which is only service pack 1. Is there a way I can upgrade to Pro without affecting the files on my HDD. Also will there be collisions involving the fact one is SP2 and the other is SP1?

Yes you can upgrade to SP2 without affecting your documents or pictures. A backup is recommended before making any big changes. It does not matter if the PC had SP1. SP2 includes everything released in SP1 anyway.

The Pro CD does not include SP2. If I upgrade will it affect it. (writing SP1 files to a system with SP2)

It may, so you should actually find an SP2 install media CD or simply create your own SLIPSTREAM install disc...

Thanks for that jmmijo. I'm getting internet on the computer I want to upgrade so I'll do it then. Thanks for your help!!!

EDIT : Just remembered to ask before I install Pro after doing this will I need to back all my files up or will it install Pro without deleting everything?