I tried to install Mandrake 8.1 for tha first time today. all went fairly well( with some bumps),till I booted up the first time to the desktop and the mouse went bye, bye. I worked all though the installation and is common serial (Dexxa brand) mouse on com 1. System is generic Pent. 200, 65M, 2.1g SCSI HD. Just my old one that I wanted to use a learning base for Linux. and leave the new 750 Duron with 98SE for now.
The mouse pointer is on screen and just slowly and occassionally drifts around. any clues?

Try to reconfigure it. I am not sure if the Mandy has mouseconfig but in RH it is in /usr/sbin/mouseconfig. Just open up console as root, issue
init 3
and login as root again
run
/usr/sbin/mouseconfig
and choose your mouse again, it might work.

Thanks for info, I'll try to follow you instructions and let you know if helps.

okm as far as i know (i had a similar problem) this is easy to fix. Since your X worked "out of the box" it is very likely that mouse protocol was not detected correctly. You can edit you XF86Config file and in the "core pointer device" section find the protocol entry and substitute it with your mouse protocol (i don't know what is the protocol for serial mice). My usb mouse uses imps/2 for example and my protocol entry is something like this:
Protocol "imps/2"
The other way is to run xf86config and reconfigure X and make sure you select serial mouse (first step i beleive) but if you dont know your video card and monitor characteristics this will probably screw up your X configuration...

Hope that helps