I deleted mine too after I read that trimming unused modules makes the site load faster. I decided to use the banners, so had the headache of figuring out how to get it reinstalled. The files are available in the source, but I actually noticed the files were still there on mine, only the definition had been wiped out. The sql code Erik submitted will actually work with a little tweaking. I got syntax and conflict errors until edited and rearranged as you see below:
SET IDENTITY_INSERT DesktopModules ON
INSERT INTO DesktopModules ([DesktopModuleID], [FriendlyName], [Description], [Version], [IsPremium], [IsAdmin], [BusinessControllerClass], [FolderName], [ModuleName], [SupportedFeatures], [CompatibleVersions]) VALUES (15, N'Banners', N'Banner advertising is managed through the Vendors module in the Admin tab. You can select the number of banners to display as well as the banner type.', N'01.00.00', 0, 0, NULL, N'Banners', N'Banners', 0, NULL)
SET IDENTITY_INSERT DesktopModules OFF
SET IDENTITY_INSERT ModuleDefinitions ON
INSERT INTO ModuleDefinitions ([ModuleDefID], [FriendlyName], [DesktopModuleID], [DefaultCacheTime]) VALUES (20, N'Banners', 15, 0)
SET IDENTITY_INSERT ModuleDefinitions OFF
SET IDENTITY_INSERT ModuleControls ON
INSERT INTO ModuleControls ([ModuleControlID], [ModuleDefID], [ControlKey], [ControlTitle], [ControlSrc], [IconFile], [ControlType], [ViewOrder], [HelpUrl]) VALUES (28, 20, NULL, NULL, N'Admin/Vendors/DisplayBanners.ascx', NULL, 0, NULL, NULL)
SET IDENTITY_INSERT ModuleControls OFF
INSERT INTO ModuleControls ([ModuleControlID], [ModuleDefID], [ControlKey], [ControlTitle], [ControlSrc], [IconFile], [ControlType], [ViewOrder], [HelpUrl]) VALUES (29, 20, N'Edit', N'Edit Banners', N'Admin/Vendors/BannerOptions.ascx', NULL, 1, NULL, NULL)