Is there a particular laptop that plays nice with Mach. I have heard horror stories of people plagued with problems trying to run Mach on them. I am looking to buy a good used laptop, but need to know what and what not to look for. Any suggestions would be much appreciated. Thank you.

The suggestion is unless you use an external controller to do the pulsing a laptop is a bad idea. Some may work and some just dont, which will or wont will be trial and error and not worth the risk. An older laptop will likely behave better but even then no guarantees.
So if you are set on a laptop get an external controller as well.
Hood