To record (eg on VHS) your PC you simply hook up the TVout lead to a SCART or VideoIn on your VCR. You can output your PC screen to a TV via the same method or do what I do if it's over a long (2m+) distance; Sit my monitor on top of my old VCR and run the TVout of my gfx card in to the SCART-IN on my VCR, then turn my VCR to the AV channel and use the standard RF out at the back of the VCR to reach the desired VCR/TV set. Standard RF leads beyond 10m are very easy to find and very cheap, excellent for watching DVDs and other movie files from your PC on your big screen TV, even when your PC is tucked away in your bedroom!
If you want to get a video signal (eg from a VCR or TV) IN to your PC then you need a card which offers VI, usually VIVO (both TVout and TVin). You simply use the same method as above and use sw to capture, encode and even tweak the signal. If your gfx card lacks VI then you can overcome it by adding almost any PCI TV card (or USB FTM). These can be had from about £30 and bring TV, if not teletext and radio to your PC, £60 should get you a more capable card with a remote control too. Look for models which encode to MPEG2 in hw if you plan to grab a lot and want to minimise file size while keeping compatability and quality. Avoid ATI, mostly due to huge compatability and WinXP driver issues.
HTH!