Hi zurzu, welcome to the forum!
What exactly is it that worked before and doesn't work now?
When you insert a blank CD-R or blank CD-RW (there's no such thing as a blank CD-ROM), are you then hoping to be able to use the builtin CD Recording function in Windows XP?
If that's what you want, you should know that this function can only be enabled for one drive at a time, and in order to enable it on another drive you need to access properties for that drive (right click on the drive icon and choose Properties...), and on the Recording tab you must check the "Enable CD recording on this drive".
The bulitin CD Recording function doesn't work with blank DVD media however - for that you need to install additional software such as e.g. Nero.