This is a really annoying problem, which is not helped by the fact that I built my own PC, and am fully expecting you all to think "sorry - but without actually seeing the machine, we don't stand a chance". But it is possible that you've seen something like this before, or have some general advice on how to go about solving it! I press the "On" button on my PC and any one of the following things might happen during boot: 1) I hear the fans start, and it all sounds like its working... but nothing further happens. (This is the point at which the monitor is normally activated) 2) It gets to the point at which its about to tell me how much RAM I have and it hangs 3) It gets to the point where there is the XP logo and the little swooshy bar and that goes on for a while, then stops and it all hangs 4) It gets to the User Login screen, and hangs - I can't move the mouse pointer Any one of the above could happen. If I take the cover off, poke and prod it a bit, then its all fine for a day or so. Then it starts again. Things which I think are probably important: 1) It seems to get quite dusty inside the box 2) The startup time (for the bit while the XP logo is screened) is getting very very long. After blowing the dust off, this frequently goes back to being exceptionally quick. 3) This has crept up very slowly. It started happening after I went on holiday and came back to find that the CD tray had been left open for two weeks. The occurences are getting more and more frequent. Having written all this down, it really looks like it needs to be taken apart, vacuum cleaned, where appropriate, and put back together. I should probably then cover the fan slots when I'm not using it. Or am I missing something else? As ever - any constructive advice will be very gratefully received! Tom

Looks very much like an overheating problem. AMD CPUs will overheat very quickly without adequate cooling. How soon it overheats is dependant on the ambient temperature. When you installed the heat-sink and fan on the CPU was it new and was the a thermal pad on the heat-sink? If it wasn't new, did you use thermal crease between the heat-sink and CPU? Did you install the heat-sink the right way round? Is the CPU fan working correctly? You can get instruction on installing the heat-sink and fan here. Stuart

Could be an overheating CPU or weak (or overheating) PSU. It could also be a RAM problem. Where is all this dust coming from? I clean the inside of my PCs about 2-3 times a year. If I open the case for an upgrade, I usually give it a quick blast with compressed air, but dust accumulation is rarely very much. Did you blow the dust out of the PSU? ASUS A7N8X-X Athlon XP 1800+ 8.5 x 200MHz 1024MB PC3200 2.5-3-3-7 Asus A9550GE/TD 128MB WinME/WinXP Pro SP2

Do not use a vacuum cleaner. They can ZAP the system with static. A can of compressed air is the best.

Thanks all I will check the cooling of the CPU - (theres a little download which can tell me if its too hot, I think). It was all new when bought, and is supposed to be fine (greased - yes) but for the sake of £10 for a new fan, this is probably worth replacing. As for the dust, I really don't know - but there does appear to be an awful lot. Its a pretty old house. I wonder if its a combination of these things, as layers of dust will presumably help heat things up - either as insulation, or by causing friction. I never blew it out of the power supply. Didn't occur to me! Thanks for the tip on vacuums - of course. I'm being dumb! As for the RAM point - I really hope you're wrong, but unfortunately thats what I kind of think is going to be the right answer. I have two sticks, so I'm going to try running on one for a week, then switching. Just to see. I've relocated them a few times, so I'm certain its not a slot - but haven't ruled out that it might be a stick. Thanks again for the pointers - I'll let you know how I get on! Tom

Instead of swapping ram in/out why not download memtest86. Sure, test one stick at a time then test both together. Takes a lot of the guesswork out of it. I used to have a signature but it disappeared and I just couldn't be bothered writing another so please feel free to ingore this.

Thank you all - and particularly Richard59. I identified a major problem with one of my sticks of RAM - so have removed pending replacement. I have cleaned and replaced the thermal paste on my CPU. I think I also have a problem with the actual on/off switch connection, but once its going, it hasn't stopped yet! Thank you very much for your help Tom