If you have old VHS video tapes, it's a good idea to convert them to a digital format. There are services that will convert these tapes for you, and send back a DVD, which may be the easiest option. ScanCafe.com will convert VHS, VHS-C, SVHS, Hi8, Digital 8, and MiniDV to DVD for $19.99 per tape. This is also a good option if you're dealing with Hi8 tapes and don't have a playback device.
If you have a lot of tapes you need to convert, it may make more sense to do it yourself. For that, you'll need a capture card or device for your computer. It's best to choose one that uses FireWire or USB 3.0, if possible. Analog video requires a lot of data throughput, and the video would have to be greatly compressed to transfer over USB 2.0 or lower. Grass Valley's ADVC110 Converter is a high quality option.