Strange box before logon

Hi, I get a strange box before I log onto my computer, I'm running xp pro, and I recently had a version of the lsass virus, I got rid of it manually, but now, every time windows loads and right before it asks for the user name and password, a strange box appears with a bunch of little characters that look like boxes, or, the Marlett font type in microsoft word when you just push space bar. There is an option to hit ok, or push the x button, the x button doesn't work, and the ok button takes me to the logon screen, once I hit ok, I see no other problems, but if I hit the x button a few times, my comp will restart, and then it'll boot up, and then it'll open another box that says "the requested operation could not be performed" and its a box for lsass.exe anyone know what is wrong with my comp? Or how to even fix it? I've looked everywhere and can't find anything, I can't do a re-install because I lost my xp cd... please, help... someone.

 

Remove dialog box before logon

Open the Registry Editor by going to Start => Run and typing in "regedit" {without the quotes}
Navigate to this key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon

Look in the right-hand pane for these two strings:
LegalNoticeCaption
LegalNoticeText

Double-click on each of these in turn, delete any text in the 'Value data' box, and click OK.
Exit the Registry Editor and restart the computer.