I have a 1TB USB HDD. When I connect it to the PC, it asks to format it. Please help!
If you have used the drive on that PC before, then the most likely scenario is that the filing system has been damaged, and you will need to recover the data.
as suggested by Paul.
If you have not used it on this computer before, it may be that it is formatted in a format that Windows 7 cannot read (e.g. HFS+, used on Macintoshes), and you will need to reformat it. Of course, you'll need to back up the data using a computer that can read it first...
The third scenario is that the disc is simply not formatted (e.g. a new drive), in which case format it in NTFS.
I think you need to recover your partition. See this article:
Also this article is good:
If you have a computer friend who is an expert, ask if they can help you go through it. Also see this MakeUseOf article. (I know the second article tells you not to use chkdsk):
go to device manager locate your hard drive driver, is there any yellow sign?
1) Open Disk Management
2) Right click on that hard drive
3) Select change drive letter and path option
4) Assign a new drive letter
Does it do the same thing on other computers or just your PC? Have you tried booting from a Linux LiveCD and accessing the drive from there? Sometimes Windows will not properly recognize a formatted drive, but Linux will. You can try recovery from there if it sees the device.