dvd witer no blank disc

hi all
can anyone help ? i have a NEC DVD+RW ND-1100A This drive will read and
play cd's dvd's but i cannot write to dvd anymore its like the drive cant see
the blank disks i insert, usually when i insert a blank disc options to open
a writable folder appear, they dont anymore, even when i use nero it keeps
tellin me to insert a blank disc, which i have! i have tried two diff types
of discs to eliminate the discs bein the problem. i only have probs when
tryin to write to disc so i am thinkin it is something to do with the burner,
is there anyway i can find out if this is the case. been through the
troubleshooter for the drive and found nothing to do with finding out if the
burner works. i have a dell dimension 4550, xp home SP2.

any help is appreciated
regards
lee.