hermbot: I've been looking for a solution for a long time and finally found something today. Using D3DWindower I was able to get PG2 running in windowed mode with Windows 7 64.
[url=http://www.filefront.com/13838785/D3DWindower-English/# ]http://www.filefront.com/13838785/D3DWindower-English/# [/url]
The program text is originally Japanese. This version has most of the important settings translated, at least enough to get you going. First, download and unpack the files (it's a .rar so you need a utility like 7zip to get at the files).
Launch the program and press the "+" button and add the PG2 .exe file to the list. Once you see it on the main screen, open the Settings for PG2 (folder icon with tools on it). Enter 1200 x 800 under the resolution and then go the Window Mode tab. De-select both DX 1-7 and "Use GDI". I've attached a screenshot.
Click okay, highlight the PG2 executable, and press the computer icon to launch the game. Enjoy!
for me in windows7 64bit i have to make it run in xp service pack 3 mode for it to start up the game