Hi, I have a dell pc that I think is called an Optiplex GX240, and when I switch it on it goes through the normal motions and then freezes on screensaver, if I press sleep and then wake up it says the comp is in use and has been locked and only windows ymtl-gmc\guest or an admin can unlock.
Using the admin name and password does not seem to help at all.
Sorry for sounding a bit on the dense side but I can work these things when everything a-ok but when it goes wrong i've had it.
any suggestions would be gratefully received. (by the way i have tried the ctrl alt del thing and it did'nt seem to work.

Have you tried booting it in safe mode? At least that way you could get in and run some diagnostics. Not sure what the key strokes are for Dells but when you first restart it should tell you.

Hi, thanks for that suggestion, on start up if i press f12 i get the boot device menu options are
1/ normal
2/diskette drive
3/hard disk drive c
4/ide cd rom device

tried normal but it still goes through the motions of loading personal settings and then the dreaded screen saver with no icons to be seen.

any further ideas most welcome

Safe Mode is F8 between the Dell logo and Windows trying to start.

Brilliant you are quite right f8 does give me the safe mode option.
Now it is that safe it won't let me do anything else though. After choosing safe mode option, i am then asked to sign in as myself or guest as normal, i then get a black screen that says safe mode at both bottom corners and i can do nothing else. Really sorry thought we might have cracked it but sadly not.
Any other suggestions pleeeeeeze

Two options you can try:

First from the Safe Mode options choose: Last Known Good Configuration

If that fails then try:

Safe Mode again but take the option for System Restore.

Choose a Restore Point prior to your problem.