Have you run Norton defrag, cleansweep? How about getting spyware and adware off the HD?
That's WinAMP agent, it doesn't use any significant CPU cycles.
You don't really give enough information to help diagnose what "slow" means. Deleting items from your Startup menu will probably only slightly speed up the boot process.
"Slow" probably means something is using up the CPU cycles, or disk access has become slow, or something is using up your net bandwidth.
I would advise you open Task Manager and see which process is taking up the CPU cycles. If there is something there you don't recognise it is probably malware and you will need to get something to kill it. You can minimise task manager to the tray and monitor it continuously.
You may want to defrag your hard disk, though in my experience it seems to make minimal difference on NTFS. Cleaning out the cr*p, like IE's cache and the temp directory, seems to do a better job.
I use all of software(s) listed below and my performance is still near a crawl, immediately following boot up. For instance, when my desktop appears, and I click on an icon, it can take up to 2 minutes for a program to start. I get the twirling hourglass for a good 90 seconds.
Help for viruses and malware: