Hoppy,
Just possibly this may be to do with small amount of data
corruption on the hard disk. This does not mean there is anything wrong
with the hard-drive.
Over time, if XP is left to it's own devices, it will accrue minor
inconsistencies along the way, if NOT checked and FIXED regularly (by using
either the option to check a drive for errors under the 'Tools' tab in a
drive's properties or by using "chkdsk /f" in a Command Prompt or "Run"
box). If using the 'Tools' option - be sure to check the box 'Automatically
fix file system errors'.
I would suggest you do this no matter what else you try, before doing
anything else. Having the drive head not be able to read a section of the
disk can cause the system to 'lock' just as you describe. It can do nothing
but good to perform a check on the drive.
After selecting [ok] (with the 'Tools' tab) or pressing [ENTER] (with
chkdsk /f) you will be required to reboot the machine.
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Cheers, Tim Meddick, Peckham, London.