External Hard Drive Dissappears after restart Plz Help

I hope someone could explain why this is happening ??

Basically i lost everything on my external HDD & the only way to get the drive working again was to format it,
That fixed the problem the drive was having (Unknown why data got lost) but if i disconnect the drive & reconnect i get message (the drive is inaccessible & corrupted) Something like that cant remember the wording exactly as its not happening right now, but i know the problem will come back & i will once again lose all my data, as its happened 5 times over 2 week period..

If i restart the PC, after startup its the only drive that's not visible either in (This PC), (Disk Management) or in (Device Manager) which leaves me with no option but to disconnect & reconnect the drive in order for it to be visible & Accessible, Now sometimes it works fine but once it becomes inaccessible it stays that way unless i format it Losing all data once again (HELP PLEASEEEE????) Its so frustrating & it cost me over £100 when i brought it from the store

Q: has anyone come across this kind of problem & how did you resolve it

In case I am asked for???
Dont know how to use event view in case you want a detailed report will need step by step insructions Please

Relevent Information of Drive

3 Years old
On 24/7 (As i never turn PC Off)
Its a Iomega eGo 1Tb External HDD

I Used software Hard Disk Sentinel & it says the drive is Healthy & in good working Condition

topgundcp said:

One possibility is If the cable is loose or does not make good contact. Try another USB cable.
FYI, external HD in an enclosure is not really designed to run constantly 24/7. There's not enough air flow and the HD gets really hot hence shorten the life of the HD.

In addition, try another disk utility such as: CrystalDiskInfo6_3_2.zip to see if it reports the same thing as HD Sentinel

I forgot to mention I already did try another cable still the same problem, & another sign that there is a problem is when i try to Transfer files the speed barely gets to 1mbps??

Right now Everything is working brilliantly the transfer speed are good & if i use the safely remove hardware Button before disconnecting the drive looks to be fixed but if i restart PC the drive is gone, nowhere to be seen on the desktop unless i disconnect & reconnect (that runs the risk of the disk becoming inaccessible like the last 5 times it happened)
Any suggestions appreciated thanks all..

Word Man said:

More specifics on drive? Bus powered portable or independently powered desktop version? Connecting via USB or Firewire?

Dont fully understand your Question! the external drive uses a USB cable (Its v3.0 i get 40MBPS)

essenbe said:

Try running Seatools for DOS long and short test on it. SeaTools for DOS and Windows - How to Use - Windows 7 Help Forums. It sounds like the drive is going bad. I presume it is connected by USB, are you having other problems with other USB connected items?

I agree with what @topgundcp said as well. Try that first.

Im trying it now thanks, Will let you know the results?