Premiere Pro CS4 is compatible with 32 and 64 bit windows 7.0. However, Premiere Pro CS5 is compatible with only 64 bit.
If you purchase CS5 master Collection or Production Premium CS5, you will get CS4 Premiere Pro 32 bit. It means that
Premiere Pro CS4 will work in Windows 7.0 32 or 64 bit.
Please refer to this Microsoft link which shows the compatibility of Adobe Products with Windows
I hope this link is help ful.