WinXp and hard drive

Having problems with my computer recognizing a HD.
Had this drive running before with data stored on it. I formated it, partioned it and made it active using disk management, assigned it drive letter J.
Initally it is there but soon disappears from My Computer window.
I have run chkdsk /r several times. When I go under my computer to view the drive it is not listed.
Under Disk Management I can see the drive but the drive letter is no longer there and the file system is blank, even though I formated using NTFS.
any help?
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Dell Dimension 4300
CPU 1.6ghz
Ram PC133 512meg
Video 64meg Geforce 2
Hd 40, 120 & 160gig
DVD LG GSA4040B
WinXP Pro SP-2
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no stress

 

Would you try control panel-> administrative tools-> computer management->disk management.