The comments above suggest that there may be a way to solve your problem without learning how to manually install LaTeX packages. But, it's not a bad idea to know how for troubleshooting, and quick fixes.
Overview:
- create a TDS directory structure (once)
- place mathtools directory inside (most packages should go in
latex/)
- run
tex on .dtx files (creating .sty files)
- (I think I've more often seen
latex <some package>.ins)
- (Optional) further cleanup towards TDS conventions
You'll want to create a texmf directory. Determining where to put it, that is, the default location, in Windows, is discussed here: packages - Where is texmf on a Windows install - TeX - LaTeX Stack Exchange.
So in your explorer, you'll want to head to your home directory, and create directories until you have the following chain:
c:\Users\<your user name>\texmf\tex\latex\
You would put the mathtools directory there, so that you have for instance
c:\Users\<your user name>\texmf\tex\latex\mathtools\mathtools.dtx
Now, open up a command prompt, and cd (change directory) to this location, that is,
cd c:\Users\<your user name>\texmf\tex\latex\mathtools\
From there, run tex on the appropriate files, that is, type
tex mathtools.dtx
You may also need
tex empheq.dtx
This will create the style files, mathtools.sty and empheq.sty.
This is enough. Latex may now know where to find the style files because of TDS (TeX directory structure). If it does not, you many have to run texhash or similar.
You could follow convention further, cleaning up, putting the documentation (pdfs) into texmf\doc\mathtools\, and put the .dtx (and sometimes .ins) files into some source directory for easy access if you want to recover them later (without internet?).
\listfilesat the beginning of your document and check the log-file. – Johannes_B Sep 11 '14 at 20:08\listfileswon't be of any help, sorry. But when the LaTeX opens a file (package, class, etc) it writes it's path to the logfile. Do you know where you installed MikTeX? Compare with the logfile for any differences. – Johannes_B Sep 11 '14 at 20:20