When you say computer not detecting
1. 98 or XP?
2. does CD/DVD show in my computer/explorer?
3. what burning software are you using? - or if XP do you use the built in?
quickest easiest is:
log on as an administrator then ....
control panel | system | Hardware | Device manager
Open CD/DVD branch and Delete the DVD entry
Then in actions | scan for changes
this should re-detect and re-load the drivers
re-boot your machine .... try again.
if no joy .... drive could be dead - or lead could have fallen out.
So now open the box and un/replug both ends of the ide ribbon (bout 2" wide - normally grey - be careful you put it back the right way round) and molex power cable (quite chunky with 4 thick wires)
if no joy .... either look on the microsoft site - there are a number of things it could be .... but need more detail.
or get yourself a new unit - �18 or so will do it