I should have posted this long ago but didn't. It is similar to the CoreDuo to Core2Duo upgrades with the Mac Minis posted here:
http://www.hondosackett.com/yabb/YaBB.pl?num=1459401997
 
I just recently acquired a Lenovo (IBM) X61 Laptop/Tablet for $25 at a Thrift store. It's an Older Core2Duo machine with Vista Windows OS but it is a machine I need as an artist station. The screen flips around into Tablet mode and it has a drawing pen for graphics programs. I just need to put Photoshop and a few other graphics programs into it as the system was erased to only its bare OS.
 
I opened it up to clean it out and see what is inside:
120GB HD @5400RPM (will be upgraded)
2GB of RAM. It's Max? Don't know but I will research it.
1.6GHz Duo2Core CPU. A Bit slow but for Graphics it is fine.
 
BUT, the CPU is on a Socket! That means that it can be swapped out with a faster CPU of the same type since Intel CPUs are internally clocked and not externally clocked.
 
In experiments with PIII and P4 Dell systems where the CPU is on a socket, putting in a faster CPU is doable and does work. Same with the Mac Minis with the Core2Dou CPU swaps. So upgrading this machine to a faster CPU should be a cinch to do. I guess within a month or so to get a faster CPU to put in there, perhaps a 2.0GHz unit.  
 
With the older PIII and P4 Dells I worked on, the upgraded system works without needing to put in faster RAM. And boy, a tiny speed increase is noticeable! The thing, many laptops, new and old, do not have socketted CPUs. Finding one is rare but when it is found, one can do such upgrades.

You need to open it and remove the heatsink off the CPU to see it is on a socket or soldered directly to the board. If it is socketted, you can do the upgrade. This Lenovo X61 I got has its CPU in a socket but from what I read not all of them do. This might be an early production model where the chip was put in at the factory on a socket.
 
BTW - many older Mac Intel Laptops are also socketted, but all of the newer ones after 2011 are soldered in. The same with the Mac Minis, after 2012 all the Mac Minis have the CPU Soldered in as well. But the older ones you can put in a 2.0GHz which makes it faster than the modern ones.... LOL!
 
While you are at it, you can blow out and clean up the heatsink and fan fins. And then replace the heatsink goo with a tiny dab of the Arctic Silver goo. That alone will fix many heating problems a old machine has as dirt tends to build up over time that is rarely cleaned out and kills many laptops.