4-5 BSOD's a day

#%$*!! I just crashed while typing this whole thing up and Firefox didn't save my tabs so I'm typing it all over again.

My self-built computer was fine for the first couple of months (built it in Sept.), but then it started crashing very often, I counted 8 times one day. It happens randomly, but seems to happen most often while watching videos on sites like Youtube or Hulu. My CPU was running hot, but the latest beta driver from nVidia fixed that. I have updated every driver I can think of, even checking them with driveragent.com. I have defragged, cleaned the registry, run anti-virus and anti-spyware, the works. I even tested each individual memory stick to make sure it wasn't bad RAM. The BSOD almost always says "IRQL not less or equal" or "driver IRQL not less or equal" and almost always mentions the file rtlh64.sys. I have discovered that that file is the driver for my Realtek network adapter, which is built into the motherboard. I contacted them about it and they just said to install the latest driver, which doesn't help. I even installed the one that they released 2 days ago. This has been going on for months and I use this computer for work (3D artist). My specs are below. Anyone have any suggestions?

Vista Ultimate x64, Core 2 Quad 2.4 GHz, GeForce 8800 GTS, 4GB RAM

Hmm, OK I'll have to look at where that option is. I know it's different for just about everyone so I won't ask for any specifics. I guess I'll just have to go without network use on this PC for a day or two. That's where Sneaker Net comes in handy. Thanks.

I do indeed have RealTek HD Audio, but that file in particular is the driver for the network adapter. I went ahead and ordered a new NIC card , Intel brand for this one. Ordered from Newegg last night and it has already shipped, so I guess I'll find out if that's it soon.