I have an Athlon XP 2100+ which I have tried for many months to cool without much luck. On a hot day with the side of the case on it will sit at about 56 C idle and upto 63 C under load. This results in system and motherboard temps of around the 40 C mark typically. Recently I have noticed the system is a little more sluggish, could this heat be causing it? Thanks in advance.

Not very likely. you might want to check your system for viruses, spyware, adware, etc.

Amd chips usually become unstable when they become too hot. But Pentium 4 chips will slow down when they get too hot. 56C is pretty toasty for a 2100+ My 3000+ is 38C Idle and 63C Load. What brand of heat sink are you using?

I have a Coolermaster cooler with Coolermaster premium thermal compound but I have quite a cheap case with poor fans and ventilation which I think is the problem.

Well there you go then.

an amd cpu either runs or freezes, there is no sluggish possibility. You must have programs in the background or a virus or spyware or a full hard drive or a bloated registry or something else. Run toast and see at what temp you lock up, if any. Because if you are stable at 69C, why worry about 63C. www.netbetty.com/toast.zip if your temps are not helped when the case is open, ventilation is not your problem, its the cooler. Get a big copper sink or the alx800 and put a normal 80mm case fan on it. http://www.newegg.com/app/viewProductDesc.asp?description=35-109-115&depa=0

Well, of course you always have to keep your comp clean. And by that I mean, free of all malicious programs such as adware spyware or any viruses. That ALWAYS helps. But, Its quite normal for an AMD chip to become stable when it gets too hot... [WHICH IS ALL THE TIME !HAH!] But that I must say, is what they are good at... HEATING YOUR WHOLE HOUSE! They use WAY too much power, And by getting a heat sink fan, you will definitely improve stability within your processor. And you also want a good power supply if you have an AMD chip. ___SamZee___