Hey people,
It was kind of rough for me to really have my website upgraded to 2.5 joomla version from 1.6. However after reading a couple of links here and there these are my versioned steps to have your website upgraded to 2.5
Step 1:
Ensure your website is with version 1.6.5 (the last update in 1.6) if not please visit get the update from this link (link to stable 1.6.5 patch Joomla_1.6.0_to_1.6.5-Stable-Patch_Package.zip).
After downloading it, unzip and copy only directories/folders (Administrator, Libraries, language) as shown in the image below:-
Paste them into your website folder/directory. Confirm from your administrator panel version of 1.6.5 as per the image below.
If YES ......... great your good to go on step 2.
Step 2:
Upgrading from 1.6.5 to 1.7.0 joomla.
Very simple just download Joomla_1.6.5_to_1.7.0_Package.zip get a file from here. Unzip you will see two other zipped files as shown below.
Go ahead to unzip Joomla_1.7.0-Stable-Update_Package.zip file. Copy all those files into your website directory/folder. When you refresh you should see something like image below:-
Now you will need to upgrade your website to the last version of 1.7 which was 1.7.5 and download that file here Joomla_1.7.0_to_1.7.5-Stable-Patch_Package.zip. Do the same as previously, unzip, copy the files from zip then paste them into your folder/directory of the website.
Step 3
Upgrading from 1.7.5 to 2.5.0
Go download Joomla_2.5.1-Stable-Update_Package from respiratory. Click here to download. After Unzip and copy all the content into your website folder/directory.
To confirm that website has changed version: Go to Site -> System Administrator -> System Information
Then go ahead to get the latest version of 2.5.x as shown on joomla website.
Now I know you will face a couple of problems with templates but each template gets a unique error message.
For example I have Yootheme template and I had to adjust one line of code in their WARP Framework
I used the answer on the link below to resolve my problem.
http://forum.joomla.org/viewtopic.php?t=637484&p=2748567