Ubrales :
Do not use the defective drive. Instead, download Recuva from "http://www.piriform.com/recuva"
Now connect the defective drive to this computer as an external drive, and try to recover your pictures.
After you do so, backup your computer frequently and regularly.
If the drive isn't showing up this won't help to much at minimum the drive needs to show up in the device manager or management console for this program to be able to function. But it seems like that isn't the case for this Hard Drive.
One thing I would check is to see if that enclosure works with a known working drive. If it isn't then it could be an issue with the enclosure and not the drive, but then again it could be both but right now we can't be sure. Otherwise if the enclosure works then you have the issue of deciding how important that data is to you money wise because your last resort would be to use a Data Recover Specialist to get that data off the drive for you.
Western Digital has a list of specialists on its site ->
http://support.wdc.com/recovery/index.asp?wdc_lang=en
I can't say I have ever needed to use one, but I think if worst come to worse then this may be your only option to recover some or all of your pictures. Its a hard way to learn but remember to invest in a Portable backup or backup drives for your most precious data.