[Sussex] Hard disk help/ XP reinstall!

[Geoff Teale]

Derek wrote:
------------
> Second, I have a friend who has a laptop with XP. He has 
> virtually never used it (it's only 6 months old and he had it 
> as a gift) but now, without any fiddling, it demands the key 
> code from the disk every time it boots and, even though the 
> approriate code is fed in, it simply reboots back to the same 
> demand. Changing to Linux, even a deb distribution :-)> , is 
> not an option. I shall look at it on Tuesday and probably 
> re-install or downgrade to W2k. Anyone any sensible, helpful 
> suggestions before I zap what's on it? There is nothing on 
> there which needs to be kept, so even reformatting is fine.

Aha.. 

What Neil is saying is probably the best answer.  However, if that fails
I've seen something like this before with Windows XP.. 

Part of the way that Microsoft determins change in the hardware platform
running Windows XP is by analysing the result of an system call to generate
a UUID.

UUID is generated from a number of factors including MAC address of network
cards, CPU ID and time.  There is a known fault with the UUID generation on
NT Systems after NT4 service pack 5 (this includes Win2k and XP) where
certain dates can cause a time dependent part of the UUID string to
overwrite a CPU ID dependent part.

This fault was listed all other the place until Microsoft had their big
strop about public sights listing their bugs (apparantly Microsoft bugs are
copyright material).

In systems other than XP this bug is reasonably harmless - the UUID is still
extemely unlikely to be duplicated (I believe the probabilty of duplication
is still 2 to the -16777056 even with this bug).  As the main use of UUID's
is unique identification this is considered a minor bug.

In XP however a change in the CPU ID returned in the UUID means that, as far
as XP is concerned, the CPU has changed and so a new registration is
required.

The specific conditions to generate this error only happen on a few machines
in a million and only on  certain dates so it could be you'll find that you
turn it on next week and it just works.. 

The best bet is just to rebuild the machine with an OS that doesn't do that
kind of checking - W2K or below should be fine if your user is so stupid as
to reject a quality free solution..!
-- 
GJT
geoff.teale at claybrook.co.uk




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