I have a samsung sw248f cdrw drive. I am trying to use it back up important data. I am using roxio (v3 i think), it came with the drive. First I formatted the disc (memorex 4x), then I go into windows explorer, go to my cd drive and create a directory, then I drag and drop the harddrive data that I am backing up, into the directory I made on the cd. The next day I do the same thing, creating a new directory dragging and dropping etc.., after a few days, sometime even a few weeks, the disc looses some of the previously made directories, the disc does not show full, so I know I am not overwriting them. Sometimes the cd just quits reading or writing and locks up the system, and won't read or write on any machine, and has to be thrown away. What could be causing this? Based on my experience so far cdrw does seem very reliable. The drive will write to a regular (non rewritable) cd, with no problems, why can't I get it to work with rewriteable? Any suggestions would be greatly appreciated!

IMHO packet writting is just unreliable and the problems you have experienced are common. My advice is to just multi-session the disc rather than packet write to it.
Starting with a blank disc, select 'start multi-session' as the disc option in your burning software & write your backup data. then each time you want to add data select the 'continue multi-session' option.

CDRs are so cheap there's no point in packet writting to CDRWs, when discs were expensive it made some sense to partially erase CDRWs for reuse but given the inherent unreliability of CDRWs and packet writting it's alot safer to just use multi-sessioned CDRs.

hth