I can't install any template

Hi,

yesterday night i updated joomla from 1.7 to 2.5 (of course without a prevous back up ).
After that the backoffice was working properly but there is no way to see the website!

After trying to re install (following the joomla instructions and not following the link in Joomla as previous did) no changment.
Than my last attempt was:
1. copy a web working with a different template (Corporate) and joomla 1.7
2. change the reference to the DB and other stuff
3. install the PIXELLOVE template.
The result is that in the template style config page i cannot see the right column and i still see a white page!
4. tried to install a different template THENEWS2 and the result is just the same in the backoffice (no right column) but in the site i see "something"

I suppose that there are some files that are not correctly deleted or update but i can imagine other solutions to restore the website...

I hope you have some suggestion.

Thanks in advace

Fabio

Update:
I've installed a different Template (GK_MUSIC) and i seen more components in the website and also the right column in the template manager (backoffice).
So maybe the problem is limited to the installation of PIXELLOVE template.

In general if you don't see any output of your website it means that some fatal error occured - usually in this case the errors are logged to file named "errorlog".