Most people have it the other way round - RH8 won't run properly on their Win7 machines and end up running it in either XP compatibility mode or in the VM
I think I saw another user report instability issues if the companion RoboSource Control was also installed. If you have RSC installed, try uninstalling it. Especially if your Windows 7 is of the 64 bit flavor.
There are many of us (myself included) that are using RoboHelp 8 quite successfully in native Windows 7. And my PC is of the 64 bit flavor.
Helpful and Handy Links
I'm running 8 without issue on Windows 7 Pro 64-bit. I don't have source control installed.