My laptop is *so* *slow*

Fairly frequently these days, my laptop just slows down to an unendurable crawl. 
Everything slows, even screen refreshes.  It is a Toshiba Techra 8200.

Per helpdesk guidance I chkdsk'ed and defrag'ed; but it still happens.  My current
guess is that when it heats up it gets slow; because it generally seems OK when I
first start using it.

Anyone else seen something like this?