Move HJT to its own PERMANENT directory.
Boot in Safe Mode
Switch off System Restore
Press ctrl/alt/del and in taskmanager try to STOP: nardx32.exe
Next, run HJT on its own and let it fix:
C:\WINDOWS\System32\nardx32.exe
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Bar = res://C:\DOCUME~1\ag\LOCALS~1\Temp\se.dll/sp.html
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = about:blank
R1 - HKCU\Software\Microsoft\Internet Explorer\Search,SearchAssistant = about:blank
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,HomeOldSP = about:blank
R3 - Default URLSearchHook is missing
O4 - HKCU\..\Run: [e054RXNqg] nardx32.exe
When done, delete C:\WINDOWS\System32\nardx32.exe
Clean EVERYTHING from C:\DOCUME~1\ag\LOCALS~1\Temp
Boot normal.
When OK, restart System Restore
Maybe you should re-install your Avast?
O23 - Service: avast! Mail Scanner - Unknown owner - C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe" /service (file missing)
Or was it due to the hijack? run HJT to see if that line is still there.