First up, welcome & well done on running Adaware & spybot first :) . Unfortunately, as you have discovered, they are unable to repair this particular hijack so please do the following:
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Bar = file://C:\DOCUME~1\Matt\LOCALS~1\Temp\sp.html
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page =
R1 - HKCU\Software\Microsoft\Internet Explorer\Search,SearchAssistant = file://C:\DOCUME~1\Matt\LOCALS~1\Temp\sp.html
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Bar = file://C:\DOCUME~1\Matt\LOCALS~1\Temp\sp.html
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Page = file://C:\DOCUME~1\Matt\LOCALS~1\Temp\sp.html
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,SearchAssistant = file://C:\DOCUME~1\Matt\LOCALS~1\Temp\sp.html
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,HomeOldSP = about:blank
O2 - BHO: (no name) - {378CF8F0-68F1-4EC6-9C4F-C1D884C5BBAA} - C:\WINDOWS\System32\hgkihn.dll
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Download and install APM from: http://www.diamondcs.com.au/index.php?page=apm
Close all windows except HijackThis and fix the lines above.
In the upper window of APM select explorer.exe
In the lower window find and rightclick the BHO from the HijackThis log
Select Unload DLL and click OK on the prompts that follow.
Reboot and scan with AdAware to remove the txt and html protocol association.