How can I view hidden characters in Notepad++?

The simplest way is to use the menu:

View->Show Symbol->Show all characters

It will show Tabs and EOL characters.

Here is an example of a VBS script that announces the current hour being viewed in Notepad++ on Win7.

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Note that it is clear I used spaces to do the indents - not Tabs.

This is the base script I used in the Q&A about how to make Windows announce the time at the top of each hour:

If you really want to get a raw look, check out the HEX-Editor Plugin (Check the Plugin Manager for it). You'll see the character codes for everything; even non-printable characters.

I use it, and have no issues on the newer versions of Notepad++.