My dad was having problems getting Picasa to work properly on his computer. Picasa was coming up in Spanish instead of English. I finally figured out the problem and just wanted to summarize it here for others with the problem. I am getting all my information from this Google Groups posting.
If you already have Picasa installed, you can got to Tools | Options | General | Language used in menus and dialogs. In that drop down box chose your language. Now the problem comes when you cannot read the language that Picasa has chosen for you. For example, Japanese. I am going to take a guess and suppose that the settings are in the same place in all languages.
Tools is the second menu item from the right (next to Help). Options is the last choice on the drop down. General is the first tab. The language can be chosen in the only drop down box within that dialog box.
If you have not yet installed Picasa (or you have un-installed it due to this problem and need to know how to fix it before installing again) you can do these steps that this poster describes. I do not have a Windows machine available to test with, therefore I cannot summarize more clearly. But if you are a Windows user, this probably makes as much sense as using Windows in the first place.
I went to Control panel–Regional & Language–Advanced, and made sure the Language for non-Unicode Programs is English. Also to Default User account settings- made sure it is NOT checked, and to Default Input Language, and made sure it is English. I was able to reinstall Picasa in English!
I hope this helps someone else who has Picasa (or potentially other software) installing in the wrong language.