Problems burning CD's

I've got a Dell Dimension 3000 with Windows XP and a SONY CDRW/DVD CRX330E to burn CD's.
My CD device can play music and read data discs but when I go to burn music CD's with Media Player, I Tunes, RealPlayer etc etc it does not recognise that I've put a disc in and burning does not start. The discs are OK because my friends can use them.
I've searched the internet but cannot find an answer to this problem.
Can u help?