该教程中的下载链接是旧版本的django注册，它与Django不兼容1.5。您应该直接从bitbucket查看最新版本，并按照说明进行。

I'm trying to install django-registration on my project using this tutorial: http://www.michelepasin.org/blog/2011/01/14/setting-up-django-registration/ but I get this error:

ImportError at /
No module named simple
Request Method: GET
Request URL:    http://127.0.0.1:8000/
Django Version: 1.5
Exception Type: ImportError
Exception Value:    
No module named simple
Exception Location: C:\Python27\lib\site-packages\registration\backends\default\urls.py in <module>, line 22
Python Executable:  C:\Python27\python.exe
Python Version: 2.7.3
Python Path:    
['C:\\Users\\Fabrizio\\Desktop\\django\\test\\gym',
 'C:\\Python27\\lib\\site-packages\\setuptools-0.6c11-py2.7.egg',
 'C:\\Python27\\lib\\site-packages\\pip-1.2.1-py2.7.egg',
 'C:\\Windows\\system32\\python27.zip',
 'C:\\Python27\\DLLs',
 'C:\\Python27\\lib',
 'C:\\Python27\\lib\\plat-win',
 'C:\\Python27\\lib\\lib-tk',
 'C:\\Python27',
 'C:\\Python27\\lib\\site-packages']
Server time:    Wed, 3 Apr 2013 09:39:44 +0200

I found some answers here but I was not able to fully understand the solution, could you please explain me how to solve it? thank you.

The download link in that tutorial is to an old version of django-registration, which is not compatible with Django 1.5. You should check out the latest version directly from bitbucket and follow the instructions there.