Update fails

Hi, I'm updating from 2.1 to 2.5 I transfered the (extracted) zip file to my /wp-content/themes folder. After uploading I get an error when I try to view my site. "PHP Fatal error: Call to undefined function simplecatch_content_nav() in E:\hansuuttwente.nl\wwwroot\wp-content\themes\simple-catch-pro\content.php on line 87" My PC does not have an e:\ drive. This error also happened when trying to upgrade from 2.3. Please advise.