best psu tester?

hello,
a while ago i had alot of memory errors and bsods.
so i got my ram replaced and was all fine until yesterday.
now im getting memory errors again.
so im thinking its eiether a corropt swap file or a bad psu giving out wrong voltages.
what is the psu tester you people reccomend?
from a UK shop.
i will use it for my pc then i will keep it in my toolkit since im a trainie techie.
thanks in advance
lodore

For voltages - A multimeter will do the job.
Put the PC under strain and take a reading.

You can also look in most BIOS's to see how stable the voltages are, although never take these readings on face value!

Anything more complex needs more complex equipment, like oscilloscope's :)