try F2.
Failing that, as the computer boots, keep pressing the tab key during and before the thinkpad logo. This will hopefully swithch the logo off and display the POST results, where you should be able to see which key to press to enter your BIOS (or consult your manual if you still have it).
Once there, see if you are able to "try other boot devices"
Failing this, if you have one, try booting from a USB thumb drive - you never know! I don't acctually know if it would work as I've never had cause to try it, but it might be worth a shot.
Let us know how you get on...