This is easy to do in Windows 7 via advanced power settings in CP. What's the equivalent function in XP? The reason I want to do this is to rescue an old overheating laptop. If I lower the max CPU state that should prevent CPU from overheating...
throttlestop v 6.0 works fine on xp.
this can be used to max the cpu mhz. (disable cpu throttle)
it can also do the opposite. (lower the multiplier)
available options may depend on the bios.
later versions of this freeware expire.
have been using this for years.
https://pixeldrain.com/u/MPAQzPKS
downloaded from the tech site and tested.
configure and place a shortcut to the exe in the startup folder.
Undervolting the processor is a nice battery and heat saver without sacrificing too much performance, and I've done it on many systems. For older chips I believe the 1ghz to 2.5ghz range I use SpeedSwitchXP or maybe WinThrottleNT. For AMD systems (what I usually have) I've seen several programs but I typically used K10Stat version 1.54. Now on my newest system a socket AM1, I only monitor temp with CoreTemp. For Intel chipsets I use RMClock which also works on AMD. All of these programs have auto and manual control, and I could send them to you.
Extensive instructions for RMClock:
https://dottech.org/4932/lower-the-temperatures-on-your-laptop-by-undervolting/
Yeah, I'm not impressed with any laptop cooling that I've seen. Some of them get so hot they unsolder themselves and completely die (looking at you HP dv6)
I don't have much experience with Vista and newer, I guess we'd have to yahoo those program names and see what OS's they're compatible with. You could also get one of those "shelf of fans" to sit under your laptop that plug into a USB port and force more air through the vents.