Hard Disk Not Showing in My Computer

Hello,

I have an external hard drive which is stop working, I have got very important information in that hard drive. I take out the hard disk from the case and pluged directly in to IDE cable then the result is took sooooo much time to boot system and finally windows open and then i look in to my computer for the hard disk but i didn't find over there and then i look in to device manager - system it is showing in there. I don't know what to do, please some one can help me.

Thanks in advance