Delta Search is ad-ware that hooks into your browser experience. It appears to leave behind a few bits when it is removed. The last bit to remove that I found is that Delta Search is launched when you open a new tab in Internet Explorer or Firefox.

For Windows Internet Explorer: in Windows use regedit then you can search for delta-search
The change is,

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\AboutURLs\Tabs

which should be as a default,

res://ieframe.dll/tabswelcome.htm

For Firefox: in Firefox go to the special URL about:config and find the parameter,

browser.newtab.url      

which should be

about:newtab

Opera Start tab doesn’t work in the same way so it doesn’t have this issue.