ImpMon tells you that you're best off replacing a writer that's more
than a year old.
Jerome Balti suggests that the problem might be in software rather than
hardware, which I don't think is likely, but it isn't impossible by any
means.
A *very* useful bit of kit is a 5¼" USB enclosure (or at least a
USB-to-IDE adaptor that can fit onto and power 5¼" devices). Covers you
against a multitude of situations, including protecting your expensive
main machine from suspect devices.
Last time I was getting suspicious of my desktop's DVD-writer,
which was about 18 months old at the time, I got a new writer in a USB
5¼" enclosure which runs at 4 times the write speed of the old one and
cost a third of what the original drive did.
2 birds, one stone.