Post the MaterialLibrary2014CMILM.log from the TEMP folder and see if it gives more details as to why the materials library is failing to install.
Thanks for replyin Danny but i don't know where to find this .log file. I downloaded the student version of revit, extracted it with windows installare and tried to install it; it crashes on the last step saying "The library could not be installed/uninstalled. Please exit all running applications and try again". I did it, closing also my antivirus. I read on this forum that it is a quite common error and i followed all the suggestions that were provided here. Still the same error with the Medium Image Library 2013. Last year i installed Autocad 2012 and everything was fine.
As I said that log file will be in your TEMP folder, something like C:\Users\<username>\AppData\Local\Temp
In the TEMP folder i have just:
There is no MaterialLibrary2013CMILM, probably beacuse the installation failed
Sounds like the MSI file for the Medium Materials Library is corrupt, otherwise it would be creating the log file regardless if it installed or failed to install.
You could run the Revit install again and when you get to the page of the install dialog where you can install the product just uncheck the box for the Medium Material Libraries. This will get Revit installed and running for you.
Or you will need to redo the download and extraction and try the install again.
I've just installed Revit 2013 from the same installation file on my other pc and everything was fine and working. But i really need it on my laptop, where i already installed Autocad 2012, i don't understand why i can't work it out. Thank you for your answers and i hope you'll help me to fix this problem somehow.
Post the Revit 2013 Setup log from your TEMP folder lets see what errors it is reporting.