+ 0 Votes Do you have a SCSI drive??? DMambo 4 years ago First off, have you wiped the drive prior to the downgrade to XP? If not, then use killdisk or another freeware app to completely wipe the drive. sym_u3.sys is an LSI driver file. If you need to load it, you need to hit F6 during Windows CD boot to load SCSI drivers.