I have my friend's hdd which crashed few daz ago then I connected it to my PC as slave but now its in the device manager and bios though not showing in MY COMPUTER,DISK MANAGEMENT.. help

Right click on Disk Management in the mmc console and select Rescan Disks.
If it still does not show up then check your BIOS settings to make sure the slave adapter is not disabled.

Just because it shows up in device manager does not necessarily mean that the drive is functional.