] Microsoft is expected to recommend that the "average"
] Longhorn PC feature a dual-core CPU running at 4 to 6GHz;
] a minimum of 2 gigs of RAM; up to a terabyte of storage;
] a 1 Gbit, built-in, Ethernet-wired port and an 802.11g
] wireless link; and a graphics processor that runs three
] times faster than those on the market today.

Follow the line:
Intel 486DX2-66, 24 megs (~1993) runs Win 95 (1995) ok.
Pentium 120, 64 Megs (~1994) runs Windows 98 SE (1998) very well
AMD K6-III, 256 Megs (~1999) runs Windows 2K, ME and XP (2000-2002) very nicely

Hell even my beastly Dual Pentium 200 MMXs, 128 megs runs Win 2K just fine. 2 year old hardware has and should be able to run modern OSes. However,even overlooking the 1 terabyte and GigE crap, it seems like a modern top of the line PC will not running an OS due out in 2 years. The amount of resources they are expecting are so far from current standards.

Contrast this with my Linux Experience

Dual Pentium III 600's, 640 Megs (2000) runs Mandrake 10.0 (2004) beautifully
Dual Pentium Pro 233's, 512 (1996) runs Mandrake 10.0 (2004) very well (yes, even X).