Windows 7 - Setup was unable to create a new partition

After 1 Day, My 320 Gb HDD is Not visible...Only 75 gb HDD is visible...
What to Do??
All wires are connected properly..

Considering 320 was visible just a few moments ago, I'd say you have a broken wire or a SATA wire twisted too tight. Wires may function today but... stop tomorrow. Or, your 320 is reaching the end of its lifespan. Or... it could be a million things.

Clear the CMOS in order to get to point zero in BIOS. If your computer has stood alone for a longer period, you might want to get a new CMOS battery. I once solved my problems with a new battery.

I have copied my all data from 320 gb HDD to my friend's laptop.. now I wanted to partition 320 gb & 75 gb Hdd..as both of them are empty now

Where did you install Windows 7?

Personally, if it was my setup, I would install Windows 7 on the 75Gb drive using the whole drive.
Windows 7 will only see and use 298Gb's out of the 320.
I would partition the 320Gb with 4 logical partitions as follows;
1st partition, 10Gb's for Page File
2nd partition, 96Gb's for pictures, videos, documents or whatever you choose.
3rd partition, 96Gb's, for whatever you choose.
4th partition 96Gb's, System Image and File Backups.
Again, this is how I would most likely set it up, the decision is ultimately yours of course.

There are a few great tools for partitioning hard drives, cloning, moving and re-sizing etc:
Free Partition Magic alternative & free Partition Manager Software for Windows PC, Workstation and Server - EaseUS. they have the free home version which works quite well and many people use it.
The other which I just came across recently from another post here, which is also free, has a few more options than EaseUS and works just as good.
Powerful partition manager and free for disk and partition management.

Hope this helps
Don

i had the same problem then i called up my system engineer and the only the he did is....
1)he entered into BIOS(by continuously pressing f1 at the very start of system)
2)he selected reset BIOS settings.
done after it loaded very successfully.
hope this works

Entering BIOS happens with a slightly different keys, my present is Delete, I've had F4 and F2.

"Resetting BIOS" = clearing CMOS. It can also be done by loosing > resetting a jumper on Motherboard, or by taking off and resetting the CMOS battery, a small round one on the Motherboard. In some cases the battery may have worn out, and needs replacement - not very common, but if your computer has been standing for quite a while... it won't do any harm to replace it.

But a good point, srujana.

Thanks. I now am able now to install Windows Server 2008 R2 by following these steps to clean my brand new disk.

Originally Posted by Saltgrass

If you do not have anything on the drives you need to keep, because this will wipe them. During the Install, on the second page where you have the option to Install or repair, use the Shift+F10 key combination to open a command window. Using that you can clean one or both drives with Diskpart. When you list the drives, just make sure you get the one you want. Type the following commands with enter after, and if you want to clean both drives, re-select the other drive to clean and then exit out.

Diskpart
list disk
select disk 0 <--this would be if Disk 0 was the one you wanted
clean
exit
exit

What I think might be going on is you have the 320 G drive set as primary and since it shows as logical, Windows cannot put an active partition on it for the boot files. Cleaning the drive will remove the logical partition.

Edit: How old is the 75 G drive. You might want to disconnect it completely.