Ok Win XP (I know it's old and about to run out of "microsoft maintenance" range.. )

I'm looking at a friends Dell Vostro 2510..

Trying to run anything on it, program and keyboard locks up after the screen goes to sleep, mouse does waken the laptop up but that's all it does, mouse moves but no clicks, no keyboard and what ever I was running still appears to be running but it's not...
Checking logs nothing obvious...

So I'm thinking "thermal" or HDD issues.... check with Dell website - I actually found a page that was helpful - go figure... I reboot it and boot into it's "diagnostics" mode...
Run a memory test, HDD test and the works - every one of is a "Pass" no fails / errors...

So what the heck is up with it.

I did run Malware Bytes on it - it did find and remove something on a quick scan - I tried running the longer scan it locks up..
Avast AV does the same on a long scan...
HDD checks out as ok via chkdsk /R etc etc... on a reboot...

Ideas Ladies n Gents,

Do I replace the HDD and clone Win XP on to it
or
Get XP to Install over itself
or
Fresh install of XP, redo the user folders, re-install everything then run the updates
or
Just replace the laptop period?