Toshiba L300-155 BSOD

Hi,

I have 3 Toshiba L300-155 Laptops and they have Blue screen problems.

Only one is particularly bad with this.

The specs are:
Intel Celeron 560 single core 2.13Ghz CPU
2GB DDR2 Ram
120GB Sata Hard drive


Two have Windows 7 Professional 64bit and the other has 32bit XP Pro.

It all started a few months ago when one just randomly blue screened, but so quickly I could not get the code. (When it was running XP)

I was going to upgrade to W7 soon anyway and thought if it was a software problem a new clean install would fix it.

But it just got worse and worse. Now you start the machine and 9/10 times it will blue screen instantly when entering windows. Then it will get further in and maby work for 10 minutes and then BS again. after 2-3 times it works for 1-4hours then will do it again.

I have Run Prime95 on it and it gave me this error after less than a minute 'rounding was 0.4 expected 0.5' (sometimes 0.4 with 8 or 9 more numbers after '0.482621818' for example)

I searched this and it came up as unstable system needs more Vcore. But ALL the BIOS setting are Locked, I cannot change anything!

I then ran Memtest86+ Which found NO errors with the Ram.

I tired a diffrent Hard drive that I know works fine but still get the blue screening.

The other two laptops dont blue screen as ofter, 2/10 chance at any random time of use.

Has anyone got any ideas?

I think the motherboard may be shot...

Thanks in advance! :)