If you are in the process of upgrading your current PC then please give us your full system details along with your upgrade budget.. Likewise, a budget figure is required in case you are setting up a new rig.. Also, please provide your area info so that we may (if possible) direct you to places (or websites) where you can get your stuff from at the most decent prices..
The best value configuration for gaming would not include a Pentium D processor, you would prefer something more modern. AMD and Intel both have some great gaming platforms for little cash layout. But as stated already, we need to know what your budget is, what are your expectations, and what games you would like to be running, on what type of monitor.
I'm sorry, I'm not versed in confusing talk . To answer your original question yes a Pentium D is compatible with win7, just don't expect it to be fast. Pentium Ds should all have 64-bit support so you can use Win 7 64-bit with them.