HDD: Western Digital WD7500AAKS, 750GB, WD Caviar.
USB Casing: TAG SATA to USB (also supports IDE->USB)

Here I'm giving my problems with an external HDD of 750GB which I converted using a TAG SATA to USB casing. Please give some time in reading it, I beg to all the experts to help.

I bought it 'bout 6-7 months ago. For about 2-3 months it ran very well and then it gave me the biggest shock. One day without any warning or ultimatum, it's format was gone alongwith 50% of data, rest of the data the HDD shad to be recovered. After this incident it started to behave non-friendly and it used to stop at anytime while running. Regardless of all that I continued to fill it up.

That incidents continued and from 2 days before posting this thread, it started to behave in very alienic ways. On some PCs sometimes it shows "USB Device not Recognized", sometimes it runs quite well whereas sometimes alongwith this, one more RAW drive appeared of 0 Bytes. I was amazed what was infront of me. Now, I beg any HDD expert to please read the following questions:

QUESTIONS:
1. Is 750GB too much to make it portable?
2. Are WD drives incompatible with TAG SATA-USB casing?
3. Did I waste my money: Rs.6700(HDD) + Rs.650(Casing)?
4. Is this the ultimate fate of such a converted HDD?
5. Are there some special precations which I must had obeyed?

Further, the shopkeeper has no clue of what might be happening, the problem is that I'm not able to show his my problems, so he is in safe-zone.

The first 3 phases of Scan disk complete succesfully, but the Phase 4 of Scan Disk (Windows XP SP2) never goes to completion. Further sometimes due to electricity problems it went under some voltage-variations and sometimes closed without safely removing. Can this be the root cause to the problem?

DECLARATIONS:
1. I live in Mumbai(India), if any expert can at least diagnose my HDD I can come to him.
2. Are there any other forums/websites from where I can get help?
3. Please post your experiences if you are also using the external HDD converted from Internal HDD.
4. I'm also ready to pay some amount for any expert help, which will really solve my problems.
5. Any other help or posted experience will be gratefully accepted.

I just found that the casing I'm using TAG 3.5" HDD Casing only supports upto 500GB. Can this be the reason for malfunctionings?

Well, my guess is the enclosure. Just because someone makes an external casing, and that it works for 5 minutes, doesn't by any stretch of the imagination mean it will be reliable. A fault anywhere in the chain (USB-SATA board, USB cable, USB port on your computer) can corrupt data. I don't know if TAG is a good brand or not, but my general belief is that they all are prone to problems. As for special precautions, don't drop it, don't tip it over, and for God's sake stop using it and back up your data when you start having problems.

What to do now? You could try removing the drive, and hooking it up to a motherboard's SATA connector. If there are still missing or corrupted files, and they are very important to you, you might be better off getting a DR firm to safely recover what can be recovered.

Thanks a lot for replying. One more thing is that I had no idea about the enclosure and what I just went to the shop and he gave me this thing. What you people are using as an enclosure, please tell me I'll buy one if it's really reliable. MUST support 750GB HDD.

I like my Acomdata enclosures. They ship their 1TB PureDrive drives in them, so 750 is supported. I got a bunch of them as a result of buying external drives and them being cheaper than internal units.

Why are you not using eSata anyway?