I have a service called omsService.exe which is taking half a gig of ram. I've googled the service but can't seem to find out what it is. Any ideas? I'd prefer to not have to shut it down every time my PC boots if its needed
Looks like it's part of MetaScan, an anti-virus product that runs as part of other programs. As I understand the marketing material at that link, you wouldn't install MetaScan as the main antivirus product on your system; rather, programmers build it into specific applications that need to be able to verify files and won't know for sure if the systems where they're installed would otherwise have reliable antivirus services.
Unfortunately, there's no clue here which other application on your system is using this service, or how it will behave if you disable it. My advice is to go ahead and disable the service anyway (