A recent post of mine about the same subject (I've also done it with a Dell U2410 at 1920x1200):
I’ve been doing what you’re trying for several years with this setup:
T60 2007-72U
X1400 GPU
VGA cable
Win 7 Pro 32bit (64 also works - never tried with XP)
Driver 8.561 (probably from TVSU or MS Update – no CCC installed)
The key is changing: Control Panel > Display > Adjust Resolution > Multiple Displays
To: Show Desktop only on 2 (or whichever is detected as the TV)
Here is a cap from my Sony 1920x1080 TV:
http://s18.postimage.org/6hff15brd/T60_x1400.jpgJohn