Are you able to get to BIOS now?

Also, with the CPU issue, have you reapplied thermal paste?

If my heatsinking was hanging off, I would clean the paste from CPU and heatsink then re-apply it.

You also need (as someone else suggested) to swap out the PSU to rule it out.

Quote from tongey :

Are you able to get to BIOS now?

Also, with the CPU issue, have you reapplied thermal paste?

If my heatsinking was hanging off, I would clean the paste from CPU and heatsink then re-apply it.

You also need (as someone else suggested) to swap out the PSU to rule it out.

1: no
2: no, where would i get the paste?
3: it has, the same happened

most pc shops would have thermal paste. less than £5 should do the trick.

Quote from anbiddulph :

i cant get to BIOS, you switch it on and nothing comes on the screen

Well, does it start at all or is it completly dead now ?

Quote from R.Kolz :

Well, does it start at all or is it completly dead now ?

complteley dead

"The Test Bed:
* Pentium 4 3.2c @ 3.73 GHz, @ 1.7 volts
* Cooler Master Jet 4 HSF - Full Speed
Ambient temp was roughly 23?C for these tests, running Prime 95 for five hours:
* Arctic Silver 5, fully burned in: 43~45?C
* Toothpaste + Vaseline: 46~49?C
* Desitin Diaper Rash Cream: 46~48?C
Wow, those results speak for themselves! Toothpaste + Vaseline and Diaper rash cream are almost equal. Choosing between the two, diaper rash cream is the obvious choice, given the fact that it doesn't have the corrosive properties of toothpaste and I noticed very slightly lower temperatures with it." * http://forum.lowyat.net/topic/706153

........

Back to topic. The CPU has thermal throttling and no overheat would ever stop it from at least starting up the PC. (99,9% sure about this).
I just tested:
Without any CPU cooler and a P4B, 2.8ghz I, after 20 secs, still can have my fingers on this CPU..

If you can´t start your PC at all anymore check:
a) all cables to the motherboard, incl. the ones for the on/off switch.
b) CPU for propper seating.

And/or: Take the motherboard out of the cabinet, connect the PSU with motherboard and test with CPU&CPU cooler only, nothing else. Find the on/off switch contacts of the motherboard and shorten them for a second to start the PSU. (Page 28 in the manual, http://www.manualnguide.com/dl/11861/ ).
If now still nothing happens, it has to be a (likely physically) damaged CPU, a damaged PSU or a defective motherboard/bios. Last mentioned would make most sense as of your description.

for anyone who is still interested in this topic i am happy to say that a new motherboard fixed my problems, everything is running fine at cool tempuratures!

2 quick questions.
1) is a load temp of 60 degrees high?
2) how much of a difference does new thermal paste make? (if it hadnt been replaced aftre the fan was taken off the cpu)

60 is getting on for being pretty warm I guess, you can never have too much cooling!

Not as bad as mine anyway, motherboard CPU fan speed control seems to be shagged, fan stopped and I didn't know until it started feeling like it was burning my leg, BIOS showed 82C CPU temp before it shut off!

My computer is still running a bit slowly even now I have proper cooling in the form of a Molex powered fan, is my CPU/Motherboard permanently damaged and needs replacing do yer think?

Quote from anbiddulph :

2 quick questions.
1) is a load temp of 60 degrees high?
2) how much of a difference does new thermal paste make? (if it hadnt been replaced aftre the fan was taken off the cpu)

1. 60 is pushing on a bit, not too dangerous if it isn't at 60 constantly though.

2. You must replace the paste if you've taken the heatsink off the CPU, as when it settles after being applied it forms an airtight seal. After removing the heatsink, you've broken that seal, causing air to block the heat's path. This could be the reason for your 60C temps too.

Quote from dougie-lampkin :

1. 60 is pushing on a bit, not too dangerous if it isn't at 60 constantly though.

2. You must replace the paste if you've taken the heatsink off the CPU, as when it settles after being applied it forms an airtight seal. After removing the heatsink, you've broken that seal, causing air to block the heat's path. This could be the reason for your 60C temps too.

ah ok thanks me thinks i need some thermal paste then cuz it can go up to 62 degrees at 100% load

Sorry for not reading the whole topic (it's late) but I had a similar thing happen to me with Windows 7 shortly after I got a new GTX 260 (1792mb version). A few days after I got the new card I decided to install Windows 7 for some DX10 carnage with far cry 2 and crysis, it all worked fine then with no hiccups. Then a few days after I took my computer to a LAN and then for the first half an hour I was there it worked fine, then I moved it into another room and after that point of the day my computer BSOD'ed 3 times in the space of about 40 minutes, and then it would restart out of nowhere every 20 (ish) minutes for about 8 hours until I decided to go home. I thought my PSU was the problem, but it ran xp perfectly before I put windows 7 on, two days later I put XP back on (after having Windows 7 on for about 3 days, I was intending on running it for much longer) and I haven't had a problem since.A few days after I put XP back on I decided to kill the doubt of the PSU and replaced it with a 1000 watt model.