I've had my computer for 7 years, and have managed to get along fine without .net framework. I know it's a download from Microsoft, and I refuse it when it's on my list of downloads. If you don't use file sharing with computers outside your home, you don't need it.

usually if you come across something that will require some specific version of .net framework it will tell you that to use it you will have to update to that version of .net. Your pc does have .net framework on it most likely I think all of them come with it but it is likely an earlier version.
If you don't use programs that are requiring it then you don't have to do it. Go to your control panel> add remove programs and look through the list you should find your .net framework listed there it is likely going to be 1.1, now if you do have version 1.1 or what ever version it states you have if any security updates come out for that version or hotfixes you should do those since you do have that version on the pc and you would want to have the loaded version kept patched.

I think there is a little misunderstanding of what .net framework is here, It's analogous to Java in that it's an engine that runs behind the scenes to provide functionality, it helps things run. It is used by certain programs many of which are involved with webpage design and display, it is used for programs like MS Visual Studio, it is also used by some game consoles, the newer applications may require the newer version of .net,older ones will be able to use 1.1 which is standard. However version 2 is NOT backward compatible with version 1.1 which is unfortunate.
it's a framework/API to allow quick development of products with less errors, like ASP.net, Office 2007 uses it, and MS has really been pushing .net on the development community so a lot of the newer applications do use .net and when you need or get one of those applications or programs it will tell you that to use it you will need such and such version of .net for it to work (it works in the background to allow things to perform their task) and it will usually offer to have you install it or give the link to install it.

here is the wiki on it, somewhat techie but does explain it.
.NET Framework

so it does not matter if you share files or network that is not what the .net means at all.

you can simply leave the one you currently have on your pc as is till some day some program tells you that you will need a newer version of .net to run it, but do make sure if there are hotfixes or patches for the version you have as I mentioned earlier you do get those. I would not advise removing it from your pc either because it is very possible something you have on the pc does use it with out your knowing it.

Thanks. It seems I do have net framework 2.0 with its(?) SP1. So now I'm wondering what it was that I told MS yesterday that I didn't want to download and not to bother me again. Ha ha. Guess I'd better make a little trip to MS now and see if there is some hotfix I need to get for it. But the latest installations connected with it on my computer were on Sept. 24, so now I'm thinking maybe they snuck everything past me while I was debating what to do and posting my question here.

On the surface, at least, I am now being asked whether or not I want to download and then install things, the way I wanted it to be.