Just rebooting the computer may help, if you have not done so already (you should at least be able to open the CD tray and read the DVD after rebooting).
Re-installing the game should not effect your saves (when un-installing you may get asked if you want to keep them, or not).
In XP the saves are in the folder
C:\Documents and Settings\ %username% \Local Settings\Application Data\Divinity 2\Savegames
or in Vista / Win 7
C:\Users\ %username% \AppData\Local\Divinity 2\Savegames
You may need to set Windows Explorer to show hidden files and folders.
