http://www.microsoft.com/presspass/features/2009/Apr09/04-28Win7QA.mspxPressPass: Does Windows 7 have higher system requirements with Windows XP Mode installed?
Woodgate: Yes. We recommend that customers use Windows XP Mode on a PC with 2GB of memory. We also recommend an additional 15 GB of additional disk space for Windows XP Mode. In addition, Windows Virtual PC requires a PC with Intel-VT or AMD-V enabled in the CPU, as it takes advantage of the latest advancements in hardware virtualization.
NOT supported on desktop:
Core 2 Duo
E4300/4400/4500/4600/4700
E7200/7300/7400/7500
E8190
Core 2 Quad
Q8200/8200S/8300/8400/8400S
Pentium
E2140/2160/2180/2200/2220
E5200/5300/5400
mobile:
Mobile CPU products
Core 2 Duo Mobile
L7200/7300/7400/7500 YES
P7350/7450 NO
P7370 YES
P8400/8600/8700/9500/9600 YES
SL9300/9400/9600 YES
SP9300/9400/9600 YES
SU9300/9400/9600 YES
T5200/5250/5270/5300/5450/5470 NO
T5500/5600 YES
T5550/5670/5750/5800/5850/5870/5900 NO
T6400/6570 NO
T7100/7200/7250/7300/7400 YES
T7500/7600/7700/7800 YES
T8100/8300 YES
T9300/9400/9500/9550/9600/9800 YES
U7500/U7600 YES
Core 2 Extreme Mobile
QX9300 YES
X7800/7900 YES
X9000/9100 YES
Core 2 Quad Mobile
Q9000 YES
Q9100 NO
Core 2 Solo
SU3300/3500 YES
U2100/2200 YES
Core Duo
L2300/2400/2500 YES
T2050/2250 NO
T2300/2400/2500/2600/2700 YES
T2300E/2350/2450 NO
U2400/2500 YES
Core Solo
T1300/1400 YES
T1350 NO
U1300/1400/1500 YES
for AMD parts
Low end sempron and athlon rev E + turion rev k8 E