If you don't use your CD-ROM player that often, your system might be assigning memory for it's cache which you could reclaim. Here is how:
1. Right click on My Computer
2. Select Properties
3. Select the Performance tab and click the File System button
4. Select the CD-ROM tab
5. Note how much memory you are assigning to the CD-ROM cache and adjust as you would like
The Minimum is 64KB (No read-ahead selected and the slider to Small) and the maximum is 1238KB (Quad-speed or higher and the slider to Large). 
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Optimizing DVD File System Performance
Digital Versatile Discs (DVDs) uses the main file system cache (VCACHE), and there are no performance settings for end users to change.
Saving Memory by adjusting your CD-ROM Cache