I just got Dell Latitute C610 and it seems to have a serious mouse drifting problem, after checking several source It seems that it is long known that the Latitute series suffers from this problem, It is even mentioned at the dell support forum.
As I nearly gave up I found a quick solution for the problem:
Go into the BIOS (F2). Press Alt-P until you reach "Page 4 of 7". Under "Pointing Device" change the setting from "PS/2-Touchpad" to "PS/2". Reboot.
The touchpad and point stick will still function as long as there isn't a mouse plugged into the PS/2 port. If the mouse is plugged in, it will override the integrated devices.
Finally I can start working.... :-)