http://msdn.microsoft.com/en-us/libr...88(VS.85).aspx
"However, users can change it by using the Advanced tab in the regional and language options portion of the Control Panel."
Open Control Panel, click on "region and language", select the "Administrative" tab. Under "Language for Non-Unicode programs:" click on "Change System Locale..." and choose Japanese.
(Now games will no longer fail to run and simultaneously restart your computer)
That is all, of course, assuming you don't need to run other non-Unicode programs in some other locale.
I've had zero issues with h-games in Windows 7 64-bit. I think anyone installing a 32-bit operating system on an anywhere near new machine today is doing themselves a serious disservice. Unless you know for sure you have hardware that won't work with 7-64, of course.
Hope that info comes in handy when your Windows 7 is installed. Afaik I did install the japanese language pack, but apparently that isn't necessary. I only note it here in-case you have issues.
7 is great, though. I've been using the RC for some time now and my copy of 7 ultimate(that I paid $10 for, thanks Expert Zone

) is on the way

Good luck!