This is something I noticed: When I use Windows, my hard drive is louder and running almost all the time.
In Ubuntu on the other hand, it runs quieter and more seldom. This even applies, when I start a windows-virtual machine on ubuntu host system and the noise goes up. I observed this on several computers and set-ups. Any ideas? Can someone confirm this?
If this is a Windows 7 (or Vista) installation, it's likely the prefetch and superfetch processes that have your hard drive moving. However, be cautioned that this could indicate a hard disk problem (such as a bad sector) within the Windows partition.
I just replaced a bad hard drive on an Acer Aspire laptop due to numerous bad sectors. The Windows partition repeatedly crashed (I reloaded the OS a few times, though getting a solid installation was futile). My Ubuntu partition ran well, even though it displayed numerous hard drive errors during boot.
To answer your first question, the hard drive will simply be more active due to the much more frequent disk I/O activity from Windows. I'm not really sure what the root cause of the increased disk activity is, but consider that the memory requirements of Windows 7 are much higher than that of Ubuntu. Therefore Windows will be using the swapfile more often, and that will result in increased disk activity.
A second cause might be the numerous 'scans' that Windows runs. This includes the file indexer (unless you've turned it off), spyware / virus scans, etc. Those sometimes run without any prompting and can really put some stress on the disk.
The third reason could simply be the filesystem itself - Windows uses the NTFS filesystem by default and Ubuntu uses Ext4 by default. My own experience has demonstrated that Ext4 is much faster at bulk file operations than NTFS. (Nothing official, but certainly reproducible.)
