As long as you are sure that all connections are as they were before it happened,this may be due to adding some software of late.
Try the following to repair.Remember you may lose some newer files or software programs if they were load when problem started.
With WindowsME, you can open a DOS window to run scanreg, at the blinking cusor type scanreg /restore, or scanreg /opt
You will be prompted to do a reboot - answer Yes(Y) as your computer must restart to finish
Before this was only available when booting straight to DOS.