I just encountered this problem myself on Windows 7 Professional x64, and a solution that worked for me was to go into the registry and edit the following value:
Location: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\sermouse
Key: Start
Value: 3
Change Value to 4 and it will stop this problem occurring.
Here is a list of all valid Start values:
0 Boot (loaded by kernel loader). Components of the driver stack for the boot (startup) volume must be loaded by the kernel loader.
1 System (loaded by I/O subsystem). Specifies that the driver is loaded at kernel initialization.
2 Automatic (loaded by Service Control Manager). Specifies that the service is loaded or started automatically.
3 Manual. Specifies that the service does not start until the user starts it manually, such as by using Device Manager.
4 Disabled. Specifies that the service should not be started.
A reg edit command would be as follows:
REG ADD "HKLM\SYSTEM\CurrentControlSet\Services\sermouse" /V Start /T REG_DWORD /F /D 4
You then need to restart the computer, which should now start correctly and not attempt to discover a serial mouse.
good luck.