PC Keeps restarting, wont go to safe Mode or logon to windows

[lino124]

Hello!
I have two HP desktop PC model: (Vectra VL420 MT) bit old, they are booth running windows XP.
resently they just stoped working. When i swicth them on, it gets to the stage where it says Microsoft Windows when the welcome screen is about to come it just restarts. I treid to go to safe mode, it also restarts when i press enter.

I treid changing HDD with new ones still restarting, took out the CMOs battery for a while still no success.
I treid to install windows, when it gets to the option press any key to boot from the CD, i press enter and it just restarts. Dont know what else to do. Please Help

[ale52]

Strip the system of everything but the motherboard / video / RAM.  Boot the system.  Do you POST?  If so, start adding one component at a time, starting with the keyboard, mouse, etc., until the system fails.  Usually the last component installed is the culprit...though not always.
 
Alan <><   

[lino124]

Thanks for posting, i did just as you said, removed everything, just left the Graphic card, HDD and the keyboard. Started the PC it tried to boot into windows, but ir restarted again, tried to go to safe mode same thing.

Please keep posting.

[gold]

Do you have onboard motherboard video, that is, separate from your graphics accelerator card?
HP shows that the VectraVL420 comes with an ATi Rage 128 Pro or Ultra PCI graphics card, but doesn't specify whether there is motherboard video.
If possible, use motherboard video instead of the PCI/PCIe card and remove the PCI/PCIe card.

Remove the hard disk.

Try to boot from the Windows XP Install CD.

[patio]

Tried another PSU ? ?
Re-applied Thermal paste ?

Thermal Paste Guide

The above doc is in .pdf format so DLoad and install Foxit Reader...

[lino124]

No there is no onboard motherboard video, it's using the ATi Rage 128 Pro or Ultra PCI graphics card. Disconnected HDD, connected the DVD/room booted from the Windows XP Install CD. Got to stage where it says "Setup is trying to Inspect your computer configuration." It then restarted, i will try to apply some thermol past as suggested