Available physical memory plummets for seemingly no reason, netsvcs to blame?

Arrgh, this has been plaguing me for weeks and I still haven't found a solution, even after perusing all manner of forums and FAQs.

Windows 7, 64 bit, here. Whenever I boot up my computer, physical memory used by my usual applications (Usually AIM, Firefox, and Windows Media Player) hovers around 1.6-1.8 GB, but slowly climbs as time passes, to 3.5 GB and upwards, slowing my PC to a crawl. It remains at that stupid amount until I restart my PC and begin the process anew. Windows Task Manager shows no memory-hogging process under the Application or Processes tabs, and I've run routine anti-virus scans from multiple apps with a clean bill of health.

Using the Resource Monitor and Process Explorer indicates that my issue might have something to do with svchost.exe, which, from what I understand, is a pretty wide umbrella of processes. The outstanding culprit seems to be netsvcs.exe, so what might my best course of action be from here? It'd be nice to have this machine running like it used to...

Screengrab of the Process Explorer is here, hopefully it might assist my case.

Thanks for your time, and any help is much appreciated!

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