Use Vuescan
If you want to use many old scanners on anything after XP and they will not install in compatibility mode(s), you must default to Vuescan scanner software which covers almost all of them. It can be run as a trial for as long as you want, but adds a watermark to scans until you buy it. They have gotten 170,000 new customers since Vista.
I have tried everything else on Vista and Win7 for a HP6200c and but there is no known workaround as a Google search will prove.
However some old scanners will install flat out in Win7, or in compatibility mode, as I discovered with my Scanwit 2720S using Windows 2000 mode, and while will not install at all in Vista.