Very often, after installing some kind of disk writing software, or, for no reason whatsoever, your CD/DVD drive stops recognizing any media inserted. The problem often lies in so-called Upper and Lower filters.
Wikipedia defines filter driver as follows:

A filter driver is a Microsoft Windows driver that adds value to peripheral devices or supports a specialized device in the personal computer. It is a driver/program/module that is inserted into the existing driver stack to perform some specific function. A filter driver should not affect the normal working of the existing driver stack in any major way. Written either by Microsoft or the vendor of the hardware, any number of filter drivers can be added to Windows. Upper level filter drivers sit above the primary driver for the device (the function driver), while lower level filter drivers sit below the function driver and above the bus driver.

Microsoft is aware about the problem with filter driver conflicts, and there is even a small "Fix-it" wizard, created specifically for this problem.

If you want to fix the problem by myself without downloading anything, here is what should be done:

• Open Registry Editor. Click Start, select Run and type "regedit".

• In the navigation pane, locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E965-E325-11CE-BFC1-08002BE10318}
  
  You can use Search function to find the mentioned subkey quickly.

• Note: before perfowming the next step, you may want to back up your registry data to be able to restore it in future.

• In the right pane, select UpperFilters and delete it. Do the same with LowerFilters.