Computer stuck on boot screen

[Earth]

I have a Windows Vista machine with Service pack 1 installed on it. It used to work fine before but yesterday at night my computer suddenly restarted and upon booting up at the logon screen it just got stucked? I waited 1 hour or so but my computer just stucked on the boot screen. Can anyone help me out?

[nitesh mehta]

Upon starting up your computer can you press or tap the F8 button to get into safe mode and if you can get their then try to do a system restore:

System Restore Tutorial
Vista Backup and Restore and System Restore points

[newtech]

If you are stucked and can only see the bar moving you can try to wait it out. Your last option is to boot from the recovery disk and see if the auto fix stuff does anything for you. 99% of the time you cant boot into safe mode, its bricked.

[Expertz]

I recommend you that if you have by mistakenly altered any BIOS configurations, set your BIOS to the factory default settings. Then, view your HDD from an outside source such as Knoppix or attach the HDD to another PC and see if you can retrieve your important data. After you've got everything you need, if you want to install Windows XP, make sure that the manufacturer provides drivers for XP, or that you can find drivers elsewhere. Boot off your OS CD and delete all partitions. Create a new partition and reinstall the OS in entirety.