My Aspire 4520 not showing CD/DVD drive in My computer.pLs help!!!!

Can you suggest which OS you are using?
Does this problem exist for all the CDs/DVDs?
Try to insert bootable CD and try boot from it and check if it works.
You can try blank cd and just write it using NERO and check.

-it is possible that you the optical drive is loose. That can be resolved by re-seating the drive itself.
-first, shut the laptop down, unplug the AC adapter if it is plugged-in then remove thte battery pack of the laptop.
-you need some small philips head screw driver to unscrew just one screw that holds the optical drive located at the bottom of the laptop. You may need to consult the user's manual of the laptop.

try cleaninf out the dvd lens...\
ur dvd lens might be dirty..
it is the main cause in many users and solved by cleaning the lens..
i can get a cd/dvd lens cleaner in computer store.....
use cd cleaner

try to remove it and start laptop and turn it off put it back in and restart it and it will install a default driver for it, hope this helps

Presuming that you've already tried add new hardware in control panel
remove the drive from the machine. normally there are a couple of screws in the base of the laptop. boot the machine and do a normal shutdown. reinsert the cd drive and reboot.

Enter in the BIOS and see in the boot order or the internal units if the dvd unit is still there. If it isn't then it's dead, replace it.
If it is then you didn't do a correct reinstall. Enter the bios again and make sure the dvd unit is the first in the boot order, boot from a Linux Live-CD like PCLinuxOS and from Computer Management/ Hard Disks  delete all partitions, format the entire disk to something else then format it again to NTFS or FAT. This is the only way you can be sure you are doing a clean install.

Try to use another DVD. you told you tried you old DVD from your toshiba. maybe is not compatible.. try in another.. then use your DVD in another laptop if the same from problem.check your board and DVD connection...if this under warranty bring to warranty..

if in Bios also can not detect this is hardware problem...

You will need to install chipset driver but it will be much better if you reinstall all driver for it.

Acer Aspire 4520 driver for windows xp can be downloaded here :

http://www.drivercabinet.com/driver-acer-aspire-4520-windows-xp/

puchase one vista cd/dvd and install no other option

Try to clean your combo head with spirit using cotton...thats all..