Beats me why anyone would want to uninstall BF1942 but I do empathise with your predicament. It appears the uninstaller has somehow been corrupted as you you've discovered.
There's a list of better uninstallation programs for when windows fails to do the job: click here
If you have no luck, you could try reinstalling the game and then uninstalling it again. The idea being hopefully the newly installed files will fix the uninstaller and thus allows you to uninstall corretly.
It's drastic but you could also manually remove the folder and references to the game in regedit but I'd be very cautious about this and consult the MS knowledge base first. I'll have a look for you on uninstallation problems but you'd do better looking yourself as I can't say when I'd get 'round to it.
Sadly, by the way, EA's support site was no use on the topic of uninstalling BF1942 if normal avenues failed so don't waste your time on it.