I am running the 5.8.5 GUI on Windows 7 64-bit without issue. I normally install both host and client on my laptop as I can then do some development offline. The only issue I have run into is that I don’t get a command line window when I’m in the localhost mode, but that’s more of an inconvenience as sometimes I like to run some tcl scripts locally with the engine extensions (i.e. msi commands, etc.).
I run the client in Windows 2000 compatibility mode on Win7. And as Administrator. Both can be set by right clicking on the the icon and choosing properties.