Using programs across partitions

I have a dual boot setup, XP and Vista on my laptop. Do I have to install a program (anti-virus for example) on both partitions or can I install it on one partition and use or the other partition?

 

If you dedicate only one partition for web/internet use, then install your antivirus on that partition, as your antivirus will check the other partition - sometimes you need to tell the antivirus to scan both partitions, but if you do that under the initial setup, it will do it automatically.
But be sure not to use the other partion on the internet, as it will not be protected , it will only be protected when using the partion with the antivirus.

 

So I can't create a third partition and install all "non-protection" programs there, with shortcuts to programs on both XP and Vista desktop. (Sorry for the question, a geek squad member told me that this works for "non-protection" programs, just wanted to clarify)

 

No, that won't work. During the installation of most programs, new entries are added to Windows registry. With a dual boot configuration, each version of Windows has it's own registry which needs to be updated for programs installed to run under that version of Windows. So, do as plodr said and install programs, whether protection or "non-protection", separately for each version of Windows. And, install them on different partitions to avoid problems.

 

As you can see by plodr, andusafveteran's comments, there can be problems.However, you can keep a sepearate partition for documents, and program 's that are not installed, nor, an operating system, as a backup partition that we call a documents drive.
This would not need an antivirus program,
Otherwise, I use HyperOs, which uses partition magic, and the way I do it, is to have partitions for Vista, and XP, save all documents, downloads, etc: to the documents drive.
If I use office stuff, I have partitions setup that I do not use on the web, and from the documents folder, I can update my programs, and operating systems, using autoupdater from majorgeeks, downloaded to the documents drive, that I can scan with antivirus.
I just do not use those with no antivirus on the web.
This has worked for me for 5 years , or, more.