Welcome to the forums,
How old is your scanner? I know my "older" scanner (Visoneer) did not work properly with PI, or many programs under WinXP. It was released and designed to work with Win95/Win98se.
Did your version PE-4SE
come with your scanner or other hardware? SE versions are Special Edition, or what we like to call "Simple" editions. They are not complete versions, they are free versions, and may have been tweaked by the hardware manufacturer to work with the specific hardware it is being bundled with.
The problem with scanners sometimes is not so much related to the program that is trying to access it, as it is with the firmware (drivers, etc, ) that the scanner uses. TWAIN is a technology that was developed some years ago, however the developers could not come up with a name for it. So what was decided, and subsequently stuck was the acronym T.W.A.I.N. or Technology Without An Interesting Name.
History class dismissed..
You might check to see if there are more current drivers for your scanner. You would be surprised at the hardware that is just purchased from the store, and the drivers are out of date.