My computer was not up to date with SP2. It is now.
I downloaded "SiSoftSandra" and run a diagnostic, should I post the results?
In spite of updating, the mouse continues to misbehave, though it hasn't totally locked up except once immediately after updating.
A fact I forgot to mention up til now. The cursor will commonly freeze up if I lift the mouse up off the mousepad, or move the wire upwards any significant amount. It probably is the mouse itself that is the problem, though I'm not yet completely ready to give up on a solution that doesn't cost money. (I really haven't got money to spend on it. :-/)
And as for whoever it was (can't remember) that suggested I had the mouse and keyboard in the wrong ports, no. They're correct. It's even got the little mouse and keyboard pictures above the ports and color coded and everything. Really, give me some credit at least.