Windows 7: How do I share updates on dual-boot Win 7 PC

I recently built an i7 based PC with three HDDs. I made it dual boot, using a boot partition on HDD 1 plus a boot (whole) drive on HDD 3; my work files are on a separate partition, and my archived data in on separate partitions again. My reason for this is because I find Windows does get corrupt easily enough and having 'double barrel' Win 7s means that when one goes down and is being rebuilt and reloaded with applications the other is available for me to work with.

However when I wipe one boot partition / HDD of course the downloaded and installed updates (including SPs) disapear. I wipe the partition / HDD because simply reloading Win 7 or attempting a 'repair' from the install DVD does not usually resolve the corruption. (My present problem is that somehow the main boot Win 7 has got its knickers in a twist in relation to either GPU or display operation - I have Gigabyte motherboard and graphics card, using Gigabyte-provided ATI Catalyst software, which my OS on HDD 1 refuses to operate, while the later installed Win 7 OS on HDD 3 operates perfectly.)



So my question is this: - how can I get the identical Win 7 OSs on HDD 1 and HDD 3 to each read the same update files, so I only have to download them once only to serve both OSs? Also, how can I get my system - perhaps by using Windows Explorer - to locate the storage of these updates etc on a particular location of my own designation, preferably in a separate partition to the actual OSs, so they don't get lost when I have to purge a corrupt boot partition?

Thanks in advance for any assistance.