Welcome to the forum!
There's no BIOS restrictions on R40 machines, so you'll be fine with a 160GB hard drive, just make sure it's PATA and not SATA, 9.5mm/2.5".
Good luck.
Cheers,
George
A31p (2653-???) P4M 2.5/2GB/250GB, 15" UXGA IPS, XPP/Mint ...the best ThinkPad ever...
T43pSFL (2668-BY8) PM 2.2/2GB/32GB SLC SSD, SATA-modded, 15" LED-AFFS UXGA mod, Win 7/Mint...my best friend...
R60F (0657-???) C2D 2.0/3GB/128GB SSD/ 15" SXGA+ IPS, Win 7...a FrankenPad toy for my twin boys...
T410 (2537-RB7) Core i5 2.4/8GB/128GB SSD/14" WXGA+ TFT, Win 7/Mint...just grabbed by my only daughter...
Z61m (9450-38U) C2D 2.0/4GB/500GB/15.4" WSXGA+ TFT, Win 7...my wife's new best friend...
...plus an iPad 2...and a ToughBook...or two...
I build FrankenPads....scary FrankenPads...
S = SATA-mod (on T43/p units only)
F = FrankenPad
L = LED-mod utilizing an UXGA AFFS LED screen
Please DO NOT PM me with requests for individual support, but post your questions and concerns in the appropriate section of the forum where other users can benefit from them as well. Thank you.