Mouse Erratic and Freezing Randomly

Hey there- I have a Dell 4300, running Windows XP pro, 384mb ram, 20 gig hard drive, 56k dialup isp etc.  I've been reading the boards looking for problems similar to mine, and while there are many like mine, some just aren't quite the same.  My mouse is a MS Intellimouse, PS/2, and I'm pretty sure it was a Windows patch, or lack of ram, or something in that order that caused this.  About 2 months ago, it was jumping all over the screen, right clicking stuff, and then it just froze.  I restarted it, and the mouse was back, and everything was ok, but a few days later, same thing, it froze.  So my solution, hopefully it's only temporary, is to restart the computer every time that happens.  However lately, sometimes after I restart, it freezes upon start up, causing me to restart again.  I once had to restart twice because it froze upon startup twice.  Slowly the problem has been escalating, and the mouse begins freezing more often, yet random and sporadically.  And I am not necessarily online when it freezes, as I use dialup.  Please help me fix this problem, it is getting a bit agitating, and I've tried to d some of the solutions on the board, but still erratic mouse.  I am hesistant to buy a USB mouse until I know or sure there is no possible solution to this problem.

Regards,

Jess