Major issue with LoginXP.

LogonXP or logon studio? there is a difference. LogonXP hacks/replaces system files, while logonstudio (made by stardock) doesn't.

Try booting into safe mode and changing the logon screen from there.

Logon Studio... how would you boot into safe mode he asks on a dell.

Press f8 while booting.

So. What's happening? What operating system is it? Did you get into the system in safe mode?

If you can get into XP in safe mode this will be the solution (from HELP and SUPPORT:

To run System Restore in safe mode
Access System Restore through Help and Support.
Follow the instructions on your screen.

Notes
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To access the System Restore Wizard, click Start, and then click Help and Support. Click Performance and Maintenance, click Using System Restore to undo changes, and then click Run the System Restore Wizard.
While the computer is in safe mode, System Restore does not create any restore points. Therefore, you cannot undo a restoration that you performed when the computer was in safe mode.

You can use System Restore to restore your computer to any restore point while in safe mode. If you cannot start the computer in standard mode, you can use System Restore to restore to a time when you could start the computer without errors.

To restore to a time when your computer started without errors, select a restore point as close to the time you remember it last started without errors.

If System Restore is suspended because of insufficient disk space, you cannot enable it by making more disk space available while in safe mode. You must restart the computer in standard mode and make more disk space available.

just go into safe mode and change the logon through logonstudio back to normal. when you do this logonstudio unloads itself and windows uses its normal logon.

Yea, if you get into safe mode, try changing to the windows classic logon, in the User Acounts icon in the Control Panel