There is no need to use XP pro...
if you are absolutely convinced that your OS is unrepairable...
all you need to do is perform a fresh install of the version of XP you
already have.

OTOH: I'm sure your system could be "reapired" fairly easily...

I've been running XP since it came out...and have never had to reinstall it.

BTW: CS3 is a great application...but to work with large files...
you should really get a dual core cpu and a mahcine with at least 2 gigs of
ram.

Try turning off the indexing service. That in itself is worse than much of
the spyware that get accumulated. To disable indexing do this:
Right click your C drive icon and select Properties. On the first Properties
Tab (General) uncheck the box that says "Allow Indexing Service to index
drive for faster file searching". Then click the Apply button. Click Ok on
the next little window that pops open that says apply changes to C:\
subfolders and files. Let the process run until it completes. If it stops
and says it can't apply changes to such and such a file because it is in use
just click the Ignore all button and let it finish. Indexing Services
creates a data base of all files and folders. It eventually become a real
resource hog. While the service may be useful to business programs it is a
PITA for home users.

Run Defrag and use the built in Windows Disk Cleanup program
http://en.wikipedia.org/wiki/Disk_Cleanup to clean the system. Avoid third
party registry fixers that likely do very little to help and may cause more
problems than are actually repaired. Adaware is fine but you may need more
than one spyware cleaner. I use the free version of SpyCatcher Express to
prevent a lot of bugs from hitting me in the first place
http://www.tenebril.com/downloads/ Once again avoid the free registry scan
as XP really doesn't need the registry cleaned in the same way that earlier
versions of Windows did.

I note you mention Norton; You will find that this is a resource hog, as is
McAfee. There are better solutions out there