It's a conflict between a recent Windows Update and HP printer or scanner
software.

See http://support.microsoft.com/?kbid=918165 for explanation and fix

Or do this:
Copy the following to the clipboard (it's all one line even if wrapped in
your newsreader/browser - paste into notepad and remove line breaks if
necessary, and copy again)
Click Start, run
Paste into the dialogue box and hit return.

==Copy below here==
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Shell
Extensions\Cached" /v "{A4DF5659-0801-4A60-9607-1C48695EFDA9}
{000214E6-0000-0000-C000-000000000046} 0x401" /t REG_DWORD /d 1
=Copy above here==