Computer cannot start up completely

[epah_7]

After I install unknown application, my computer only can start up till logon screen and then it restart and restart back. Could the unknown application that I install, contain virus and crash some data of my OS?

[Fahad]

Possibly it contain some virus.
Try uninstalling that software through "Safe Mode" or Use System Restore to restore your system.

[Raymond]

It could be virus but there could be other factors as well such as conflict with installed software or drivers.

[blackrose]

Thats right, there could be some conflict and most of all viruses can be causing the problem.

I hope you can login to Safe mode, first uninstall the program that you recently installed and try to restart the computer in normal mode, this should help you. Still cannot call in the BEST antiviurs and run it with latest virus update.

[epah_7]

Thanks but I reinstalling Windows XP because at that time the instant answer..