It's not a virus scanner. It's Windows thinking there is something wrong with the sdcard's file system.
Try this:
- Look in My Computer and make note of what drive letter Windows has given your phone. If you're not seeing your phone mounted as a drive, then there's a whole other issue going on than what this tries to fix.
- Click the start button and in the Search/Run box type "cmd"
- At the command prompt type: chkdsk driveletter: /r
So if your phone was labeled drive "G" you'd type: chkdsk g: /r
This shouldn't affect or hurt anything. It's just clearing the checkdisk bit that Windows set on the drive the first time it was plugged in. If you're paranoid, you can back up everything on the sdcard to your computer before running it.