I bought a seagate 1 terabyte hdd yesterday and installed it into my win xp computer successfully it showed up in my computer as well. I took a backup of my computer onto it and formatted the other HDD and reinstalled windows. Now when I inserted the new hard disk again, it shows up in device manager but not in my computer. I had created 4 partitions in it.
Any help in this regard would be greatly appreciated
thank you.

First off did you leave the HDD attached when you installed windows? If so there are time windows does not like this one at all. This can give problems. Check to see if your hdd is in an active and not inactive state. If inactive state you can set it to active.

Second you can try to turn off your system. Take the HDD off by just unplugging the cable to it. Reboot your system without the HDD attached. Then turn it off again. Now attach the HDD and boot again. See what happens.

Third move HDD to a usb port and see if you can read it from there

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Iorana Haraharaini

No I disconnected it before installing windows I have an HP and the recovery dvds would have erased it if i hadn't.
Secondly, the hard disk is enabled both in bios and in device manager.
And yes i tried what u said about rebooting it asked to connect to the net to find drivers for new hardware and said no drivers better than the ones installed found.
I'm not able to try out the usb thing as I dont have an external casing, moreover the market is closed tomorrow and i'm in a bit of an emergency.

Can you see the partitions in Disk Management?

Could we see the partition table and boot sector with Microsoft's Sector Inspector?
http://www.users.on.net/~fzabkar/SecInspect.zip

Extract the above archive to the one folder and execute the SIrun.bat file. The procedure will generate a report file named SIout.txt which you can then upload to a file sharing service so that we can examine it.

No it comes up as dynamic foriegn under disk management.
I even tried connecting it with via USB(as an external drive) but to no avail.
Please help i'm at a risk of loosing 10,000$ worth of data(My brother is a sound engineer and all his data of numerous bands is backed up onto this drive)

Well I manged to get all my data back thanx to test disk.
I'm crying tears of joy at this pont.