|Apparently " 750gb acomdata" is an external drive. |
Have you dropped the external drive since it last worked properly ?
If so, the external enclosure, and possibly the hard drive inside it especially if it's a 2.5" drive rather than a 3.5" drive, may be damaged.
External drives connected by a USB (or firewire) connection must be plugged into a port that can actually supply 500ma.
If the external drive has a 3.5" hard drive inside of it, you must connect an external power adapter to the external drive enclosure and that power adapter must be working.
External drives will often NOT work correctly if they're plugged into a USB hub that plugs into one USB port directly connected to the mboard.
If you are using a cable that did not come with it to connect it to the computer, it may not be adequate.
If you have unplugged the drive while Windows was running without clicking on the Safely Remove Hardware icon and STOPping accessing the drive, you may have damaged the data on the drive. In that case, you can usually fix that problem by using certain programs to repair the data damage.
Troubleshooting USB device problems including for flash drives, external drives, memory cards.
See Response 1:
If the hard drive that's inside the external enclosure drive is still not recognized after you have checked out those things in at least Device Manager - Disk drives and Disk Management, power spikes or surges generated by a power failure event can damage the laptop or anything connected to it, when the AC adapter was plugged in at the time, especially when you did not have the AC adapter plugged into something that protects it against damage caused by power spikes or surges .
If the acomdata external drive enclosure's circuits are damaged, usually there's nothing wrong with the hard drive inside of it. If you replace the external drive enclosure with any brand of new one meant for the same type of drive - SATA or EIDE, 2.5" or 3.5", the hard drive inside the enclosure will probably work fine.