When you try to attach a file in a custom form on the Web site in WSS 3.0- Error Message: “This form was customized not working with attachment”

When i tried to attach a file in custom list form(CustomNewForm.aspx) i got an error message :“This form was customized not working with attachment”

 This is a know issue. here is a smart workaround for this

1. Download and install Infrastructure Update for Windows SharePoint Services 3.0 (KB951695)
2. Then follow this article http://support.microsoft.com/kb/953271
3. Voila!  it works  fine for me.