Google offline data location on your computer

Windows XP

* Internet Explorer: C:\Documents and Settings\\Local Settings\Application Data\Google\Google Gears for Internet Explorer
* Firefox: Database files are stored in the user profile directory. C:\Documents and Settings\\Local Settings\Application Data\Mozilla\Firefox\Profiles\{PROFILE}.default\Google Gears for Firefox
* Google Chrome: Database files are stored in the user profile directory. C:\Documents and Settings\\Local Settings\Application Data\Google\Chrome\User Data\Default\Plugin Data\Google Gears

in reference to: Offline data location : General Info - Gears Help (view on Google Sidewiki)