CD/DVD rom drive problem

[Tefler]

When I put any of my pre-recorded disks in the drive (Philips DVD +- RW DVD8531), the machine does not read them.  This includes two games, a set of maps and an audio CD.  A CD I burnt myself the other day is fine, however.

When I put the disks that don't work in, the machine says 'Whirr, clunk" four times, then stops.  In My Computer, the CD Drive is recorded, but not the CD that's in there.

Is there anything I can do to sort out this problem?  Because it's happening to so many disks, I don't think it can be a fault in them - and they've all worked on this machine before.

[MargeB]

Try a lens cleaner.