This could have different causes. Try some of the following:
Reboot your PC, then try it again.
Delete everything thatīs in \Documents and Settings\<user name>\Local Settings\temp.
Delete the DVD drive from the Hardware Manager, reboot, then XP redetects the drive, perhaps it works after that.
Try another CD/DVD.
Remove Starforce:
http://onlinesecurity-on.com/downloads/sfdrvrem.zip