I have my students using Portable Miktex 2.9 with Texmaker. And the entry on the ps2pdf is
I have both Texmaker and Texstudio configured on my clip and I use successfully the exact same entry.
I configured my clip initially on an XP box and then copied it to a server so students could download it to their clip. It successfully runs on XP, Vista, and Win 7 both from a clip or with the folder copied onto the computers hard drive.
The important item is that your configuration for TeXStudio and all other software required must not touch the registry or access any programs connected to the registry. (In XP and Vista this was not a tightly enforced, but Win 7 has a much more diligent internal security model. [a good thing])
As a side note: I still have not been able to do a non-portable install of MikTeX 2.9 on any Windows 7 machine on my campus because of the additional security options selected (so far I can not get a waiver) by the University System Admin.