Pair up the right processor with an SP2 edition of Windows XP (Microsoft's Windows Server 2003 with Service Pack 1, Red Hat Enterprise Linux 3 Update 3 and SuSE Linux 9.2 also offer NX), and your system should run just as it did before in daily use. We have yet to see any programs break on an NX-enabled machine.
No idea. Can't even get to the link as it requires a subscription / registration. And, it involves giving not just my name and email address but a whole host of other information about my job/position/responsibilities etc that would take more time to fill in than it took to write this post. Also, there's a four page legal "User Agreement" to read ... something I just didn't have the stomach for.
The Washington Post can feel free to read this post without registering here.
The specs you quote above can be had for circa $1,000.