If you are planning to use 64 bit windows 7, I suggest you re-install all your programs to use the 64-bit version. I'm not sure if this will give you more room. I believe it will probably take up the same space. But if you are using a 64-bit OS, you want to use a 64-bit application for compatibility and performance.
I know the windows outlook for 64-bit is still being supported by microsoft. The 32-bit version, they stopped updating it, so if you are looking for a more stable version I suggest moving to the outlook 64-bit version.
I do not recommend you using 32-bit outlook with win7 64-bit.