Re: An IBM Thinkpad in 2015!
A 2007 ThinkPad T60 has a removable CPU I believe (so could potentially be upgraded), I suspect the latest chip for it would be an early Core 2 Duo of some description (it'd be nice if somebody else could confirm that as I'm not too sure), but if you can, pick up one of the Core 2 Duo models anyway, I'd suspect it'll be cheaper than upgrading it! Preferably 2GHz or greater if you want the higher spec.
The T60 was the last of the IBM branded machines I believe, and should come with a hard drive using a SATA interface so it wouldn't be a problem picking up a new hard drive for it (or possibly an SSD)
Athlon II x4 645 || 1TB 7200rpm HDD || EVGA GTX 650Ti OC || 8GB DDR3 RAM || Windows 7 Home x64
i5 4210M || 500GB Samsung EVO 850 SSD || GeForce 825M || 16GB DDR3 RAM || Windows 10 x64