Don't ignore the possibility of a bad tape especially if it's old or frequently played/recorded over. Sometimes the actual tape itself will stretch or shrink or be "scrunched" in certain areas which will make it appear/sound as though the machine is rolling it at the wrong speed. Try another tape.
If this happens on tapes recorded at EP mode, your VCR may not detect the speed of a recording on it's own-you may need to switch it manually. Try playing an SP recorded tape and see if it plays that properly. If your VCR *normally* auto selects tape speeds on already recorded tapes (this is always set manually prior to recording) then there's some sort of electrical problem that needs to be addressed before you can play EP recorded tapes again
A belt may have slipped off of it's pully and is now riding the wrong part of something else which is therefore moving the tape, but at the wrong speed. A properly working tape recorder will either have mechanical relationships or electrical regulation circuits that will keep the speed constant. Open it and look inside to see if you can find anything obviously wrong. If you don't see anything, there's probably a more obscure problem which I can't help you with- call a professional or just toss it.
