Disk space and RAM are totally different and should not be confused.
After I reformatted my Win7 Pro 64 bit to Win 7 32 bit I have only 2.75 GB Usable Memoty RAM in Computer
As for your 4GB of RAM and now you only see 2.75 that is for 2 reasons. First, 32-bit operating systems are limited to 4GB but because of how 32-bit Windows maps hardware in memory, you typically only "see" around 3.2GB. Second, you most likely are only seeing 2.75GB because you most likely are using integrated graphics and not a separate graphics card. With integrated a big chunk of your system RAM is stolen... err... "shared" for graphics processing.
Bottom line is you probably should have stuck with 64-bit. Then all 4GB would have been usable - though...
