Random restarting

Hello,
I have a windows XP computer that has just started randomly turning off.
This is mainly from when in windows, but then will take 3 or 4 attempts to restart.
I have run a disk check and nothing was flagged up, I have turned off unused services. Malwarebytes doesnt find anything or cause a crash, same with SuperAnti spyware.
I am unable to run the defrag as this causes the restart. I am using Auslogistis Defrag. Is there any defrag system that will record the last file attempted to defrag so I can see if this i a problem?

Or is there something else I can try?

 

What's the age of the PC and any newer components?

It reads like it could be a PSU or motherboard fault that's developed.

When it gets into Windows next, could you scan through the System log to see if there are any clues there?

 

The PC is 6 months old, all built at the same time.
In the system log there is nothing to report.

I was thinking possible PSU, may swap it out with a spare one. The PSU was a cheap 500W one that came with the case for £25.

Also would how it is connected make a difference? should it be connected directly to the wall?

 

Hmm, a cheap '500W' PSU might be the equivalent of a good 300-350W unit - but it's longevity would depend on several factors, build quality being one of them. Is the spare PSU a good or better one?

What's the full spec. on the PC hardware?

Providing your wall socket/extension lead and socket are all good quality with tight connections, there shouldn't be any problem with power feed from a 2-3KW AC domestic supply. Best to use a UPS in between if you can though.