DVD writers won't recognize RW disks

I have been running into this problem on two different computers. I
can read a previously written-to CD-RW or DVD-RW in a DVD-ROM drive,
but the same disks can't be read by either of the writer drives. When
I try to open the drive in Explorer, it say "E:\ is not accessible.
Incorrect function.".

The only affect that I can seem to have on the situation is to check
"Enable CD recording on this drive", in the the drive's properties.
Then, I can "open" the disk in Explorer, but it says that the disk has
0 bytes used and 0 bytes free space.

Both computers use WinXP. They are a Pavillion a1130n, which is still
using the stock HP DVD Writer 640b, and a Presario 6300US, to which we
have just added a Lite-On DVD Writer DH-20A4P98C. Both OSs have all MS
updates.

NVM I found a firmware update for my 640b, which solved the problem.

This is probably going to be the problem with the other drive as well.