DVD-R not reading?!?!

I have an Inspiron 8200 - had it for years. It reads CDs fine and also DVD-ROMs - (i.e. the discs you get on covers of magazines etc.). It also plays DVD movies OK. However, it doesnt seem to read DVD-Rs - not sure if it ever has. I have checked to see if it can read DVD-Rs it it can - its a Toshiba SD-C2502 I have tried one of the discs copied on a work PC and it reads fine - but it is another DVD Writer so wasnt a proper test (if you see what i mean). It of course reads on the original writer it was wrote on. Any ideas?? It could be the cheap DVDs - BulkPaq ones Thanks