I built my rig back in 2007 and it has been going strong until recently. As of late, all of my games are locking up about every 30 seconds. Any game will run smooth until it locks up, and it will have 1 fps for about 5 seconds then return to normal. This happens on every game, I even tried lowering counter strike to all low settings (I could previously run maxed with no problem) and the locking up still occurs. My PC runs fine when no games are open.
I was monitoring task manager with minecraft open and I noticed the the cpu usage spikes
to 100% when the lockups occur. This leads me to believe it is a cpu problem and not a memory paging problem. Also I have 2gb of memory and it is never close to being full when the locking occurs. I checked my temps and my cpu is sitting at 75C.
I tried uninstalling my anti virus and even did a full reformat. I now only have windows and a few games on to test performance and the locking still occurs. I might play around with overclocking my cpu but I haven't done anything like that for awhile and I wanted to hear what you guys had to say first. Currently everything is at stock speeds.
75C is well into the realm of overheating. Might not be the cause of your problem (probably is), but it is not a healthy temperature. Your CPU will not last long with temps like that. I'd recommend replacing the thermal paste (may have dried out over the years), and if that doesn't get those temps down into the 50s at least, buy a new fan for it.
If you overclock your CPU with the temperatures where they are now, you'll get at best a meager overclock, and stand a very good chance of permanently damaging your chip. Those temps are very worrying, fix them immediately.
Also, 2GB of memory is only going to be enough memory if you're running Windows XP. I know you said your memory isn't close to full when the lockups occur, but what exactly was it? Your computer will rarely use 100% of the available memory because it has to have some available to allocate should processes request it. Instead your computer will fall back on virtual memory and page files when you run low, which ruins your performance. At this point, you're basically using your hard drive (the slowest component in the system by a factor of 10,000) to extend your memory.
Get your temps under control and at minimum double the memory in your system. This will probably get you back to normal.
From there, I'd recommend overclocking the E6600. It's one of the best overclocking processors ever made, and I have one myself. I don't have the more up to date revision, one of the original 2.4 GHz models. It's perfectly happy running a 50% overclock to 3.6 GHz, though I keep it at 3.4 to prolong its life since it's already so old. You'll need something way better than the stock Intel fan to see that kind of overclock though, the chip gets pretty hot.