Microsoft has two versions of Windows out today, the home version is XP, the business version is Vista. Linux has many, many versions, but the primary, flagship version is Ubuntu. Apple has some interoperability between itself and both of the other systems but essentially if you want an Apple computer, it's because you're working on projects that don't really need to interface with other systems, i.e., graphic design.
Do Windows XP and Ubuntu Linux interact?
We-l-l-l, that depends on what you mean by that. Can you install a Windows program like Frontpage or Powerpoint onto an Ubuntu operating system?
Ubuntu comes with Open Office, which is very similar to Microsoft Office. Ubuntu has many other programs which are very similar, but no, you can't take a Windows program and install it onto Ubuntu.
Can you open up and use Windows documents, like a Powerpoint presentation on an Ubuntu operating system?
There may be a problem with documents created via more complex programs, such as with graphic design or database programs, but straightforward word-processed documents or basic spreadsheets will have no difficulty being translated.
Creating HTML, or Internet-readable documents, is a bit of a special case. HTML was specifically designed to work on any and all operating systems. If you download or call up a document that's been written in HTML, then no matter what kind of operating system you've got, you should be able to read it. I use the program Mozilla Seamonkey to write HTML documents on both my Windows XP desktop computer and on my Ubuntu Linux laptop computer. The program comes in both "flavors," Windows and Linux, but the documents that I create don't need any obvious adaption procedures to be written on first one machine and then the other.
So yes, there's a high degree of interoperability between Windows and Linux operating systems, but they're not identical. There is a very high likelihood that a document written on one operating system is readable and writable in the other, especially if the document is written in HTML.
Update: a buddy of mine responded to reading the above: "Good job! But one question: why do you use Mozilla to create your documents rather than Microsoft Office Word ?" My answer:
When I do my weekly report for new visitors to my church, I do it first in Linux Open Office Spreadsheet, then I keep the original copy and create an exact duplicate in Microsoft Excel (as everybody else has MS Office). The OO sheet is about 10 kilobytes, the MS Excel sheet is over 100 kilobytes! The balance is all just excess code. Worthless filler. I've seen the same thing happen in MS Word vs Mozilla Seamonkey. This is a real problem for modifying a document on the web (Besides being harder to pull up or download, the prawnworks.net home page is about 150 kilobytes as it is) as I often go into the code to find and fix problems. Having so much filler just makes it more difficult.
I'm completely unimpressed with MS Word as when I copy an article and save it to read later, Word takes all the indents out! It doesn't copy the article in a way that I can distinguish the speaker from lengthy quotes. Very aggravating as the blogs I read very frequently use indenting.
Did I mention you shouldn't get me started on why I prefer OO to MS?
And my buddy then wrote back: "I promise I won't do this anymore!