Analysis / Computer Seems To Run Abnormally Slowly

Ignore the siggie info; the problem is on a separate computer, a Compax laptop. There is 256MB physical memory and 2GB virtual memory. The C: disk has heaps of room on it.
It has Avast AV, Spybot, Adaware and Spyware Blaster and uses the XP firewall. All are up to date and all come up clean when checked. I do a monthly defrag and have Easy Cleaner and empty unnecessary files and surplus registry entries monthly. Despite all this it seems to run abnormally slowly, particularly when bringing up onboard stuff like OE, IE and other programs. Downloading internet sites seem pretty reasonable.