Unfortunately that's a very old model made by Umax and the only drivers they released for it were for Windows NT 4, Windows 2000, Windows XP and Windows 2003 Server.
Umax no longer support that model so there will never be any new drivers for it. You need a new scanner if you want to scan on Windows Vista, or it may be possible to get it working by installing scanning software called
VueScan if you are prepared to pay for it ($79). You can run a trial version first to make sure it works with your scanner. It incorporates it's own generic scanner driver which works with 99% of USB scanners. Go here:
http://www.hamrick.com
If you do decide to try VueScan, remember that you can only use your scanner by opening and using VueScan since it does not support scanning from within a graphics application (in other words, it doesn't include a TWAIN driver).
However, unless your scanner is/was a very expensive model, $79 dollars is probably too steep when today you can find new printer/scanners which cost less than that, or certainly for only a few dollars more. The choice is yours.