Does anybody know of software or of functions in e.g. MS Word that allows you to use tags in documents?

It would be helpful if I could organize my notes by creating tags (e.g. 'speculation', 'investment', 'prediction') at the bottom of a note, so that if I do a tag-search (if I want to write an article about a subject for example) I get all the documents in which those tags occur. I think that will be faster, more efficient than a regular word-search

any help would be appreciated

The windows search tool will work. Just put a prefix like # before your tags to differentiate em from regular text. Like,

Note: Speculators kick ass! #speculation

Then search for files containing #speculation

that's a most brillint low-tech solution! thank you

Google Notebook is a free app that consists of user-defined folders ("notebooks") into which you paste notes (a note is a rich textbox). The notebooks are listed along the left margin and most of the rest of the window shows the notes in the current notebook. You also define tags ("labels")and apply them to each note as appropriate; when you click a tag in the tag list, the main pane is loaded with notes to which the tag has been assigned. Everything can be searched via Google.

excellent! esp. re the tags. Thanks dude!