Changing the language list on Advance search page is very simple, just follow these steps.
Step 1: Go to Advance page, site actions and then edit page.
Step 2: Now edit advance search box web part and collapse properties section.
Step 3: Copy xml from properties textbox and paste it in any xml editor like Visual Studio so we can modify it easily
Step 4: Search for languages tag and remove any language that is not necessary from the list. For example let’s remove all languages except English from the list, now it should look like
<Languages> <Language LangRef="en" /> </Languages>
Step 5: To add another language, just add another Language element with LangRef attribute. Values for LangRef attribute will LangID from the LangDefs element. For example if we want to add Arabic then our Languages element would look like
<Languages> <Language LangRef="en"/> <Language LangRef="ar"/> </Languages>
Step 6: Copy the entire xml and paste it in properties textbox in advance search box web parts (Where we initially copied the xml from) and save the page.
That’s it we are done.
I hope you find this post useful. Thanks