Help- LITEON SOHW-1653S suddenly burning 1/4 speed

My Liteon SOHW-1653S has suddenly started burning v. slow - approx 2.3x [on Nero Speed] vs proper 8x - 12x. - takes 25-30 min to burn DVD instead of 8min.

System: AMD 1800
WinXP
Disks Verbatim.

Could it be drive?
Or software problem?
Win Explorer has suddenly started opening folder for drive when disk is inserted - which I’d stopped [but can’t remember now how to do] to speed up things. Don’t know if that’s related.

Thx for any help/suggestions.

P.S. Just as slow when no other activity on computer

Have you checked the DMA for the IDE controller it is on? It might be in PIO mode instead of DMA.