I recently installed win 7 Home Premium on a home built computer. MSI 760GM mobo,AMD quad core 3.0 ghz processor, 16 gig DDR3 ram, Nvidia 8400, 512 meg video card, and a 600 watt power supply. I have XP, win 7, PCLinuxOS, and Peppermint one Linux installed on a 500 gig HD. My question is, I got 3 updates on Monday, and one update today on win 7. Is this normal to get updates out of cycle? I was under the impression that updates were once a month.

Yes, it's perfectly normal to get updates between Patch Tuesdays.

I've noticed that too, that at work I frequently get updates on Windows 7.

You don't need a 600 W power supply to drive a AMD quad-core and GeForce 8600. I don't know what brand/model of PSU you have, but its better to pick a high-quality high-efficiency PSU of 300-500 W over a low quality 600 W.

16 GB is a lot. But the DDR3 RAM prices are very cheap. I would perhaps go with less, just so that there are less components that can decrease system stability in case of failure of one RAM module.

The 8400 is a very old card with poor performance, not good for gaming. But if you're not gaming its alright (but old, several generations behind).