my xp comp worked for ages then suddenly hung now all i get is message "during last boot up your system hung for improper frequency combinations....... i tried turning off but just get that message, i have no idea what system specs
If this is a desktop press Del key as the computer starts and go into the BIOS screens.
Somewhere there you will find settings for CPU and bus/memory. If you're not sure what to do it will be safer to go for default settings.
In fact most BIOS screen also have an option to reset all the computer's settings to a mode which will ensure that the computer starts -- may not be as quick as its potential performance but it should work.