I was going through the database because of an error I have with my portals and i did find this:

I do not see any relations on the other 2 skin tables (SkinControls and Skins). This is just inside the SkinPackages table. I wonder if deleting these 2 rows would be safe (no foreign key anywhere or so that would mess up the structure). Would the container also prevent my SKIN to not be able to delete it? It seems like that package really never completely installed.

After removing the 2 rows from the SkinPackages table, the following error pops on the HOST->extensions page and it does not display the list:  (tried removing them from Packages table too after getting error)

AssemblyVersion: 5.1.4
PortalID: 3
UserID: 46
ActiveTabID: 464
ActiveTabName: Extensions
RawURL: /tabid/464/portalid/3/Default.aspx
AbsoluteURL: /Default.aspx
AbsoluteURLReferrer:
UserAgent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; WOW64; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; InfoPath.2; .NET CLR 3.5.30729; MS-RTC LM 8; .NET CLR 3.0.30729)
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: 9a4499f6-c4dd-401d-b247-8213030c8c2d
InnerException: Object reference not set to an instance of an object.
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: DotNetNuke.Services.Installer.Packages.PackageController.CanDeletePackage
StackTrace:
Message: DotNetNuke.Services.Exceptions.PageLoadException: Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object. at DotNetNuke.Services.Installer.Packages.PackageController.CanDeletePackage(PackageInfo package, PortalSettings portalSettings) at DotNetNuke.Modules.Admin.Extensions.Extensions.grdPackages_ItemDataBound(Object sender, DataGridItemEventArgs e) at System.Web.UI.WebControls.DataGrid.OnItemDataBound(DataGridItemEventArgs e) at System.Web.UI.WebControls.DataGrid.CreateItem(Int32 itemIndex, Int32 dataSourceIndex, ListItemType itemType, Boolean dataBind, Object dataItem, DataGridColumn[] columns, TableRowCollection rows, PagedDataSource pagedDataSource) at System.Web.UI.WebControls.DataGrid.CreateControlHierarchy(Boolean useDataSource) at System.Web.UI.WebControls.BaseDataList.OnDataBinding(EventArgs e) at System.Web.UI.WebControls.BaseDataList.DataBind() at DotNetNuke.Modules.Admin.Extensions.Extensions.BindGrid() at DotNetNuke.Modules.Admin.Extensions.Extensions.OnLoad(EventArgs e) at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace ---
Source: