What makes my comp slow?

Question

I am coming from a much slower machine, this new one doesn't feel nearly as fast as I had hoped.  Used to have an Athlon XP 1600, single 7.2k RPM drive, 512MB RAM.  Now I have Athlon64 3000+, RAID 0 on 10k RPM drives, 1GB ram.  The computer barely feels faster.  The load times are almost identical.  
However, from what I can tell, my benchmark scores are within acceptable range.  I wonder if I need a faster CPU to really see that performance boost I was looking for?  Mostly I want to decrease application loading times.  It thought it was a result of slow HDD but these new ones don't really speed it up much.  I do notice that when opening many programs my CPU utilization gets pegged at 100%.  I assume if I got a faster CPU so it didn't peg at 100 the load to would down.

Answer 1

Could be a lot of things.  However, if you're benchmarks are good then it's probably just your imagination  
Other than that, my first guess would be spyware and/or virus.
1) Make sure you have a firewall installed and configured and working.
2) Install all Windows updates if that's what your OS is.
3) Chkdsk and Defrag
4) Run, update and scan with
Adaware SE
Spybot S&D
CWShredder
Antivirus
5) Repeat step 3 until all problems are gone.  You may need to do it in Safe Mode to get rid of persistent stuff.  Don't worry about the "DSO exploit" reported by Spybot S&D, it's a known issue with Spybot, and as long as XP is up to date, you're not in any danger.
6) Chkdsk and Defrag (yes, again)
Good luck.