harddisk not mounted after installation of ubuntu 12.10 in place of windows 7

Depending on how you installed it you may have lost the data or it may be just that the drive needs to be mounted.

Open a terminal (CTRL+ALT+T) and give us the output from the following commands

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lsb_release -a; uname -a; sudo fdisk -l; mount | grep ^'/dev'
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If the drive is still there we will tell you what you need to do to mount it

hi Warren ,please find the detailss

akhilesh@akhilesh-Inspiron-N5010:/$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.10
Release: 12.10
Codename: quantal
akhilesh@akhilesh-Inspiron-N5010:/$ uname -a
Linux akhilesh-Inspiron-N5010 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
akhilesh@akhilesh-Inspiron-N5010:/$ sudo fdisk -l

Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00059a33

   Device Boot Start End Blocks Id System
/dev/sda1 * 2048 618999807 309498880 83 Linux
/dev/sda2 619001854 625141759 3069953 5 Extended
/dev/sda5 619001856 625141759 3069952 82 Linux swap / Solaris
akhilesh@akhilesh-Inspiron-N5010:/$ mount | grep ^'/dev'
/dev/sda1 on / type ext4 (rw,errors=remount-ro)
akhilesh@akhilesh-Inspiron-N5010:/$

hi Warren ,please find the detailss

akhilesh@akhilesh-Inspiron-N5010:/$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.10
Release: 12.10
Codename: quantal
akhilesh@akhilesh-Inspiron-N5010:/$ uname -a
Linux akhilesh-Inspiron-N5010 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
akhilesh@akhilesh-Inspiron-N5010:/$ sudo fdisk -l

Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00059a33

   Device Boot Start End Blocks Id System
/dev/sda1 * 2048 618999807 309498880 83 Linux
/dev/sda2 619001854 625141759 3069953 5 Extended
/dev/sda5 619001856 625141759 3069952 82 Linux swap / Solaris
akhilesh@akhilesh-Inspiron-N5010:/$ mount | grep ^'/dev'
/dev/sda1 on / type ext4 (rw,errors=remount-ro)
akhilesh@akhilesh-Inspiron-N5010:/$

This is finding a single 320GB drive all of which is allocated to Linux. I hope your backups are in good order because the drives appear to be gone.

Does this sound consistent with the specification of your computer?

You may be able to get some back using foremost in a live CD. I have never used it personally you make recover something but not all.

when i was installig ubuntu....have chosen replace windows option

is it the problem

Yes.

You were given the option to install along side the existing OS, replace it or "something else".

When you selected replace it took the whole drive so you lost everything. If you had selected "something else" it should have been possible for you to replace your old C drive but keep the data on the E an F drives.