Queer mouse problem

[needhelp]

Okay this is the problelm, I recently upgraded a friends computer and in the process "borrowed" a stick of RAM from an old computer that I have. No problem the upgraded computer runs just fine. Now I bought a stick of RAM to replace the one that I had taken from the old computer and it boots up okay with one exception, the mouse just freezes, wont move.
Now this is the queer part, the only way I can get the mouse pointer to move is by doing this, using the keyboard I go into control panel and add new hardware, the wizard starts to do its thing and tells me it is ready to search for new plug and play hardware. I press the enter key on the keyboard, the wizard does its thing and the mouse starts working without any problem.
Thats fine, but when I reboot the computer it does the same thing again. I have tried to update the drivers for the mouse but it tells me that the best driver is already installed.
It is an AT mobo and the mouse is a serial mouse. running with a 466 Celeron processor.
I have removed the mouse in system properties device manager and the same thing happens it reinstalls the mouse but it still freezes.When I try to update the drivers for the mouse it says the best driver is already installed for this device.
I am not very familiar with keyboard strokes so if you have any advice guys keep it simple if you can.
The computer has been left on the shelf for about 2 weeks before I installed the new RAM. cant see the RAM would be the problem here though cos everything else works okay.

[glc]

If it has 2 serial ports, try the other one. What version of Windows is on this thing, and does it have an internal modem?

[needhelp]

Windows ME and no internal modem or external.
Computer is set up exactly as it was before.
I booted it into safe mode and everything works okay when i did that but when I boot up normally, it still freezes up. but can still use the keyboard

[glc]

Try a system restore.

[needhelp]

Tried that, no success. still have the same problem. I also reinstalled ME over the top and still no go.

[needhelp]

Problem solved I found an old floppy disk with a serial mouse driver on it and installed it and hey presto, it worked. seems that windows installed a driver for a PS2 mouse. seems strange though that it worked okay in safe mode. Oh well, thats computers. Thanks for helping glc