Windows 7 driver for ATA Hitachi HTS725032A9A364

while installing ubuntu I tried several things including formatting the partition and keeping it as a free space. Every time the partition size was displayed differently on windows and ubuntu. So I guessed something is going wrong, but didn't realize it will corrupt windows7 partition as I have selected the free space and installed ubuntu there.
I haven't tried formatting the windows partition before windows 7 reinstall as I wasn't sure that will really solve the issue. Are you suggesting me to try that and reinstall windows7?

HP have a recovery partition to reinstall from, unless you have trashed it when installing Ubuntu, you did make a set of backup dvds from within windows didn't you, no, I thought not!

Windows isn't looking for a sata driver for the hdd, but for the chipset, surprised that it doesn't pick it up automatically, as my sons G72 does this, but that could be becasuse its a Dell disk and not a standard OEM Windows disk.

I haven't taken any backup. I did contact HP and they sent a detailed procedure to recover it from HP recover manager. After that I tried reinstalling it again with the same Dell CD, this time formatting all the partitions used by windows earlier. To my surprise it just worked! I tried installing ubuntu again to check whether it would be able to detect the partitions properly, and that worked fine too. Things are fine now, but I have no idea why first ubuntu installation failed to detect the partitions and windows complained saying it can't find any drives.

Best answer selected by sathishpy.