Hi
This sounds like a virus issue to me first for the windows defender error you can follow this link
http://support.microsoft.com/kb/931849
And for the removal of dale search from your notebook please follow this link, it contains detailed step by step process with screenshots. Beware this is not supported by HP.
http://malwaretips.com/blogs/remove-dale-search-toolbar/
Once you have followed all the steps I would recommend you to get a good Anti-virus S/W to your PC