BLULOO  Buy new hardware? Want to reinstall your registered coolbook app?

The developer will tell you you're out of luck.

Neat little app but the dev says registration is only good for a specific machine.

You have to pony up more $$ for another license.

Lame policy for an otherwise useful app.  
(Version 2.14)

SAMPLER  CoolBook does much more than fan control. It can be used to decrease voltage, at no cost to processor speed, and thus it can reduce power consumption and heat. It looks like a must for the new MacBooks. See:

http://www.edn.com/blog/400000040/post/1890037389.html  
(Version 2.10)

HYBSTER  You should be aware that the author of the program insists on a strict "one machine" license, you will only be able to use this with one computer. If you upgrade, you will have to pay again. Stupid policy? Up to you...

"The license is for one computer only."

-Magnus Lundholm  
(Version 2.9)

JKAHAN  Excellent product. I just installed it on my Macbook Air and no longer have heat or core shutdowns. Search the posts on macrumors for "underclock" and there is a good thread comparing everyone's coolbook settings.

The GUI could use some work though....  
(Version 2.8)

TOMASX  This app is well worth the tiny price. I have used it for almost a year now with a 17" Macbook pro (core 2 duo). The default settings left it running fairly hot, but after spending 20 minutes figuring out the minimum voltages needed per frequency I had some settings that have been totally stable.

When you're on battery you get much better performance and use less energy, by setting the voltage to the minimum but the frequency to the max that voltage can power (for me this was almost double the CPUs normal minimum).

and for desktop work you can use the max CPU speed with a big cut in power, meaning less heat and nose from fans.

In case it helps someone out, my settings turned out to be; 1837MHz-0.95V, 2004Mhz-0.9625V, 2171Mhz-1V, 2338Mhz-1.05V.  
(Version 2.3)

DELARUE  This is not shareware as it is not possible to use the programs functionality before buying a license. Without registering, all controls are disabled and only the current CPU frequency, voltage and temperature are shown.  
(Version 1.1)

SPOKEN  Coolbook made my first generation Macbook Air usable! I was running WinXP under VMWare, and before CoolBook, this configuration came crawling to an overheating near standstill... I had concluded that the Air was pretty much unusable for my needs.

After installing and configuring Coolbook, the Air performs very well in this configuration - and amazingly, the processor seems to thrive on the minimum settable voltage at every possible clock speed.

$10 saved my MacBook Air. So what if it's locked to a specific computer? It's $10. Buy it again for the next laptop.  
(Version 2.15)

TRONDAH  Does not work in latest Snow Leopard seed. Kext does not load in 64 bit mode. It loads in 32 bit but kextcache parameters changed, complains about wrong arguments in the logs.  
(Version 2.14)

MHOLLIDAY84  My Macbook Air would always get really hot, and the video would start skipping when watching shows on ABC.com. With Coolbook, I was able to reduce the temperature of the core so that it wouldn't shut down and mess up my stories. used 0.9 V for all except 1600 MHz, for which I used 0.95 V. This software did exactly what it was supposed to.

I have a feeling that the reason some others didn't get as good of results as I did, is that they either don't know how to use the software, or they don't have their laptop on a flat surface. Remember that temperature transfers fastest from solid to solid vs. solid to air. My in-table for instance acts as a heat sync.  
(Version 2.14)

PEN_SQ  The 2.13 update is severely broken on my 2007 white MacBook (with i950). The first hint is when it is required to redo registration. After that, my voltage settings were lost. After rediscovering and entering the voltages, I didn't see Coolbook do anything useful with them.

I uninstalled and went back to version 2.12.   
(Version 2.13)