Laptop my friends toshiba has suddenly started freezing he cant log in and then cant turn the thing off apart from holding down the power switch. he can get so far then nothing! any ideas?

I have the same "computer" qosmio f60. I've replaced the hard drive, installed a new window 7 OS, changed RAM paging, power options, run the things with a fan pointed at the computer fan.
The fan goes to high speed and the HDD LED unblinking. I've brought the laptop to two computer shops whose owners knew less about computers than I did. I tried to go to a Toshiba recommended shop in Toronto except they changed to Apple-service only. I tried phoning Toshiba, they just want to change 4 bucks a minute for technical assistance. I've had this Toshiba-thing going on 3 years with the troubles starting after the first year. No one cares about this problem. If I see a Toshiba factory I'm going to chuck this red brick of cra through the window.
BTW it's not a virus or rootkit. I had to learn how to partition a HDD sector through some crazy BIOS program before installing windows. There's no virus or rootkit that's causing this problem.
It's mostly been freezing on me with games.

virus infected

press and hold off button.... switch off at main power point (remove battery if Laptop)

• Disconnect all the power supply (battery and power cord) and attachments.
• Press and hold down the power button for 30 seconds
• connect with the power cord only
• restart the computer

It seems the video card is not supporting the game's video requirement

Try this:
Turn it off.
Disconnect power cord and any other device attached to it.
Take battery out.
Without anything attached. Hold down the power button for 10-15 seconds.
Connect the power cord only.
Hold down F2 (while it's off)
Turn it on while holding down F2.
Let go of F2 when something comes out of the screen.
If multi colored lines still appears.
You have either defective LCD(screen) or video card.

Check the settings for sleep and standby times. It sounds like you are going to one or the other of these modes. Also, holding the Power switch down for 10 seconds will force a shutdown.

Go to Control Panel and User Accounts. See if it will let you change the type of account you have to administrator or if you can creat an new administrator account. If that doesn't work log off and try logging on as Admin or admin (try both) and leave the password window blank. See if you can log in under admin and then change your current user account to administrator. You also don't have to run the ISP software to get on the net. You can change the settings to your network adapters manually without software. Problem here is you might have to be an administrator account to do that also.

you have a driver problem most probably safe mode only installs essential drivers. check the log files to see where the boot is freezing.

Enter Safe Mode with Networking.
Update Video drivers.
Restart the system in normal mode and if still no go then you have to reinstall Vista from CD's.

First clean the fans out - these get clogged pretty easily.
If it gets stuck where you cant turn it off - hold down the power button for 5 seconds.

Hopefully the system hasnt been overheating for so long it has damaged the CPU or motherboard.

If the fans are clean and it still does it, you may have a bad stick of ram or the mainboard you bought may have problems.
I would inform the company you got the mainboard installed that it is having problems right away in case you dont have much time left in warranty.

Good luck!