- Login to your phpMyAdmin, export the Joomla 1.5 _users table as CSV for MS Excel with tick on Put fields names in the first row
- Open the exported file with MS Excel.
- Delete the gid column and save the file as CSV.
- Go back to phpMyAdmin, select the Joomla 2.5 _users table.
- Click Import, select Format as CSV, change Fields terminated by with comma (,) instead of semi-colon (;) to avoid the error while importing "Invalid field count in csv input on line 1"
- Click the Browse link and check the imported data.