Sometimes simply restarting your PC will work.
If not, try running System Restore and resetting your PC to an earlier date. (Go to Start > Programs > Accessories > System Tools > System Restore). However, don't be too surprised if your PC reports that it can't restore to your chosen date. (I've had very little luck getting System Restore to work under Windows ME).
Next try running Scanreg. To do this, you need a boot floppy. If you've not already got one, go to Start > Settings > Control Panel > Add/Remove Programs > Startup Disk > Create Disk). With the boot disk in your floppy drive, restart your PC. Assuming that your BIOS is set to boot from a floppy first (which is usually the default setting on a PC running Windows ME), the computer will boot from the floppy, instead of loading Windows. At the prompt, type 'Scanreg/fix' (without the quote marks) and hit 'Return'. When you get back to the prompt, restart your PC.
If none of that works, try reinstalling Word from the original disk.
Chris