Every time I download a patch and then run it, I always get the message "Heroes of Might and Magic V is not installed. Patch cannot be applied.", But I have installed the game on my computer. What is wrong and does anyone know how to fix it?

I'm having exactly the same problem, did you ever get an answer?

Thanks

Check the faq in the heroes v discussion section.

I have the same problem and the faq didn's help me :-|
I've tryed many patches for US or EU versions but it didn's worked.

Where I can find help with HOMM IV: Gathering Storm?

It is very important to install the correct patch for the version of the game you have. There are several different versions of the game available to US customers. If you have downloaded your copy of the game from Direct2Drive or Boonty, you will need to install the correct patches for that specific download version. You may also need to know if you have a European version of the game. The easiest way to know which version of the game you have, is to check the technical support information listed in the back of the game manual. If the address is a UK address, you have the European version of the game. If the address is a US address, you have the US version of the game.


US Retail CD version - v1.01
US Direct2Drive Download version - v1.01
US Boonty Download version - v1.01

US Retail CD version - v1.02
US Direct2Drive Download version - v1.02
US Boonty Download version - v1.02


If your game is from the UK or Australia, please use the following patches:
UK v1.01
UK v1.02

If your game is the 'Collectors Edition' from the UK or Australia, please use the following patch:
UK Collectors v1.01
UK Collectors v1.02


You can also install GameShadow and not have to worry about which version of the game you have or which patch you need. GameShadow will figure it out for you!

Click Here for link to patch downloads

My game is in french and the adress given is in France. So it's the European version ! I tried many patches but no one worked.

I had the same issue with the patch I downloaded off of the website. If you use the link to "Update" in your game folder, it should work.
Start Menu>All Programs>UbiSoft>Heroes of Might and Magic>Update