the drives on my dads laptop can be exchanged anytime. you just pull out the cd drive, then pop in the floppy drive. not that you'd ever use floppys anymore
I don't think it affects anything. I've always noticed the CDROM drives are listed under the devices you can "Stop" in Windows XP's Removable Devices icon in the system tray.
This happened to a new Dell. I pulled out the CD-ROM while computer was running and then put it back in. At that time I had never tried the CD-ROM. Later, for the first time, I tried to use it to install a program and the light would flash and I could hear it running but it would not read ANY CD.