So i got this vhs tape from 1991 that still function well and i wanted to convert the data on it to full hd and watch it on pc without destroying the quality
and what have you found on the topic so far?
Is the video on the tape a famous title, or some private recording?

Mind you, you can capture anything in full 1080P, but that doesn't mean you're going to get a better quality.
As Nabs referred to, although you could convert VHS to 1080p HD video, you won't get any better quality than VHS.

Your VHS quality is probably about 335x576 pixels (since I'm guessing it's PAL), so that's all the data that's there. Going up in resolution just duplicates data, giving you a larger file size.

Now, you probably still want to convert it to digital video. To do that you'll need something like a "capture card" that can take in a VGA signal and convert it to a digital format on your computer. You'll play it through a normal VHS player and plug that into the capture card.

I don't have any suggestions about what you should use or get, but that should point you in the right direction. Some digital camcorders can take an RCA signal and convert it too, so that's another option.

Hope that helps!
if you have a dvd recorder you can connect the vhs to the recorder and record it as dvd, if you want to covert it to 1080p you have to put it in your computer and convert it to a single video file with xilisoft dvd to avi converter, after that you have to load it with xilisoft video converter and convert it to 1080p (which would be useless) and lastly if you want to play back on a blueray player you have to convert it to blueray using xilisoft avi to dvd converter, note that you cannot burn that 1080p to dvd files and a dvd disc because dvd does not support that resolution (unless its a hd dvd)
thanks everyone
first of all its private and yes its pal
and when i mean better quality i meant like the up-scaling of the ps3