I'm using the 32-bit version of it. For some reason it's telling me I only have 3.75 GB of RAM available when my MBP has 4GB.
32-bit has an addressing limit of 4 GB (that includes video card memory, which is why it drops to only 3.75 GB for you). There are some tweaks out there that change the number to show 4 GB, but that's all it does as it'll still only be able to address 4 GB.
The solution? Switch to the 64-bit version. 64-bit also has an address limit, but it's artificially set at 16.8 million terabyte. 32-bit: 4 GB. 64-bit: 16.8 TB. Yeah, insane. From
Wiki:
Some operating systems reserve portions of process address space for OS use, effectively reducing the total address space available for mapping memory for user programs. For instance, Windows XP DLLs and other user mode OS components are mapped into each process's address space, leaving only 2 to 3 GB (depending on the settings) address space available. This restriction is not present in 64-bit operating systems.
Many, many people both here on this forum and in general have switch to 64-bit (for just this very reason, but there are other benefits as well) a while ago and have no issues.