Welcome to the forum.
Ex-factory your T61 looked like this:
T61 (8895-2FU)
T7300(2GHz), 1GB RAM, 80GB 5400rpm HD, 14.1in 1024x768 LCD, Intel X3100, CDRW/DVD, Intel 802.11agn(n-disabled), Bluetooth, Modem, 1Gb Ethernet, UltraNav, Secure chip, Fingerprint reader, 6c Li-Ion, WinVista Business
You'll want this Middleton BIOS:
http://www.mediafire.com/file/f9w4kv0k3 ... -1.08).rar
If you want to use the .ISO, you'll also need a new CD/DVD drive... (yours is bad)