Yeah, if you were still using it up until recently, then it has had a good run. (I still have one BNIB!)
While you CAN get motherboards for it (ebay has some P35/P45 Gigabyte "Ultra Durable" ATX boards for $60-80), I would hesitate to go down that road, unless you have some expensive software installed, and you can find an identical replacement board (that won't trigger some sort of re-activation of said expensive software).
If this is just a home / media center / tertiary rig, then retire it.
The Q6600 was great, in its day, but these days, you can get a recent Celeron dual-core, that probably has nearly as much compute power. (Kaby Lake really does have great IPC, and they are clocked higher than the Q6600 was, at stock.)
Heck, check out my recent LLano thread, you can get an AMD quad-core APU with a 2.1/2.4 clock, that can be BCLK OCed, and you can get a "modern" Win8 Ready mobo with SATA6G and USB3.0 (A75) for $45 shipped from ebay, and you don't need a hot, expensive VGA card to run it, either.