(a) Try restarting your PC before checking or doing anything.
(b) If you can't see your drive in My Computer or Explorer, hit F5 to refresh the list.
(c) Try updating Windows. Also try updating your CD/DVD playing and burning software.
(d) Look for an issue on your CD/DVD drive or your system's manufacturer's site. There may be a new issue caused by a Windows update.
(e) Update the firmware for your drive from your computer's manufacture site or the drive manufacturer.Make sure there are no disk issues like incompatible disks e.g. DVD in a CD player or burning a disk at higher speed than is possible with the disk.
(f) Another disk issue: can the disk that you are trying to read, be read from another computer or is the disk damaged?
(g) Also make sure the disk is right side down.
(h) Make sure the drive is correctly configured in the BIOS. If the drive has been manually configured previously, try setting on "Automatic".
(i) Also try updating the BIOS.
(j) Purchase a "CD Lens Cleaner" and see if this will run in your drive. These are specially designed CDs with brushes on the bottom that will clean the read and separate burn laser (if there is a separate one) of the drive. It's better not to try cleaning the drive with a compressed air because laser are delicate, but as a last resort it may be OK.
(k) Another strategy is physical: open the PC cover and make sure the power and data cables are securely attached to the drive.
(a) Here are some quick freeware tools to try if you don't have time.