I'm shocked that Stercus Vultus hasn't jumped in and said buy a mac yet!
If you are running XP try this first:
How to Fix svchost.exe using 100% CPU / Memory Leak | Technibble
If that doesn't speed it up then look at a new computer. I don't have any image software yet so I don't know if you will need a new computer but I would try the above first.