From: Milla Janick
I think you can probably get a 9800GT for about the same price as this card. The 9800 is faster, and will be a better value.
Windows XP won't be able to use all 4GB of that memory. You will need Vista x64 to take advantage of the full 4GB.
Did not see mention of a budget cooling system.
Ensure your UPS has more power than your PC.
Milla, your recommendation for the graphics card may be spot on, and dual cards are not all they are cracked up to be. [Have phone # of tech support handy.]
RAM: Aye, there's the rub. Does SL run on x64? Or maybe there is an OS that will take advantage of 4GB other than MS? Hmmm . . . wonder what that might be . . .
Windows 7 will be released, sometime, and then you will need to upgrade equipment again. BTW, even the Beta is better than XP, and I'm now using it as the primary OS [but i already have a super computer

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This post must be related to running SL. No?
If so, go with at least 32GB RAM.
7200 RPM is a bit slow to keep SL running properly.
What is the broadband speed? Since most folks use computers for Internet access, a super computer is still dependent on access speed and related server connectivity. 100gps might be sufficient.
Don't load any unnecessary programs other than the OS and SL
Don't use the standard LL viewer, find one that works.
I admire the home tinkerer, and am one, but unless one has the know it all of parts compatibility, then it is wise to to take it to someone who does. Or, do some research and buy off the shelf, and ensure you can switch out components to upgrade later.
How many times does someone, in a similar "build it myself mode," end up cursing what seems like what should have been a good idea, and paying someone to fix it? Not a budget computer then.
One last word of caution, why the need to build one's own? At some point even if everything works out, there may not be a noticeable difference in speed depending on your application usage.