Right-click My Computer, and then click Manage. Under Computer Management, click Disk Management. In the right pane, you’ll see your drives listed. CD-ROM drives are listed at the bottom of the pane. Right-click the drive or device you want to change, and then click Change Drive Letter and Paths. Click Change, click Assign the following drive letter, click the drive letter you want to assign, and then click OK.
As far as temp goes, I have a faster CPU than yours and it is reading 27 degrees right now. It probably depend on room temperature though.
Best nvidia drivers are at their main site.
Since you have a 6600GT, get this update. It will give you a temp readout of your video board and provide better support. It looks like we have similar setup besides the hard drive difference.