DANGER WILL ROBINSON - DANGER!

Before ya go changing all your settings all over the place and impacting on your system speed ... first things first ...
As Phil said, Windoze ... sorry ... Windows ... dynamically allocates space to a system "swap" file. This is used as memory for low access count items (i.e. program instructions that are not regularly accessed, that sort of thing). As your hard drive becomes full, there is less spare space for it to use for this memory and things will come grinding to a halt, as it will have to assign these less used items to system memory (which is precious stuff), or deny access to it for some programs ... which is when it all falls down.
You say all you do is browse and play the arcade ... what you possibly don't realise is that when browsing, there is lots of information stored in the background (i.e. a copy of every picture you view, so that if/when you view that page again, it doesn't have to download the image again, therefore theoretically speeding up the loading of the page) - this is also coupled with the phenomenal amount of personal data that windoze stores about you and your usage (hence why no matter what, windoze systems slow down after a couple of months of usage ...)
So - First thing to do, as A friend said, check your free disk space. As a rule of thumb, you should always have at least double your system memory free on the drive plus as much spare as you can afford. E.g. If you have 1Gb of RAM, you should have at least 2Gb of free disk space to allow for the swapfile.
Next, benign stuff like cookies and browser cache very quickly fragments on the drive, due to the constant read/write cycle. Empty your cache ("temporary internet files" as Microshaft calls them ... though for them to be temporary the system would need to delete them once in a while!), clear your cookies, check your disk for downloads you no longer need and generally have a spring clean.
After doing that, set the disk to defragment .. even if it says it doesn't need it. Walk away, go have a picnic, go shopping, have multiple cuppas etc (best bet is to leave it going overnight).
Once you have done all that, the "Virtual memory errors" should just vanish ... or at least for a good while. When they come back, wash, rinse, repeat as required.
Of course, the way to avoid all of the above problems? Simple .... Go Linux!
