Hi and welcome :).
Please uninstall Web_Rebates from add\remove programs. Windows AdTools also, if there.
Scan with hijackthis and tick the boxes next to all the following entries, then close all browser and explorer windows, and hit the "Fix checked" button.
R3 - Default URLSearchHook is missing
O2 - BHO: LocalNRDObj Class - {00320615-B6C2-40A6-8F99-F1C52D674FAD} - C:\WINDOWS\localNRD.dll
O4 - HKLM\..\Run: [Windows AdTools] C:\Program Files\Windows AdTools\WinAdTools.exe
O4 - HKLM\..\Run: [ujoonfrcd] C:\WINDOWS\System32\sucnurs.exe
O4 - HKLM\..\Run: [salm] c:\temp\salm.exe
O4 - HKLM\..\Run: [wbon] C:\WINDOWS\wbon.exe
O4 - HKLM\..\Run: [WebRebates0] "C:\Programmi\Web_Rebates\WebRebates0.exe"
O4 - HKCU\..\Run: [Bsol] C:\Documents and Settings\amministratore\Dati applicazioni\siso.exe
O8 - Extra context menu item: Web Rebates - file://C:\Programmi\Web_Rebates\Sy1150\Tp1150\scri1150a.htm
O21 - SSODL: System - {38EBE8B5-9327-44DB-B466-C2F401F8EB01} - C:\WINDOWS\system32\system32.dll (file missing)
Reboot into safe mode following the instructions here & navigate to & delete the following if found:
C:\Program Files\Windows AdTools-folder
C:\Programmi\Web_Rebates-folder
C:\WINDOWS\System32\sucnurs.exe-file
C:\WINDOWS\wbon.exe-file
C:\Documents and Settings\amministratore\Dati applicazioni\siso.exe-file
In order to view these files you may have to select 'show hidden files/folders.' Instructions on how to here.
Still in safe mode, Clear out your Temporary internet files and other temp files.
Go to Start > Settings > Control Panel >Internet Options.
Under the General tab click the Delete temporary internet files,
delete all Offline content as well. Clear out Cookies.
Also, go to Start > Find/search > Files or folders > in the named box, type: *.tmp and choose Edit > select all -> File > delete.
Empty/delete the entire contents of the C:\Windows\temp folder and C:\temp folder, if you have one. (Contents but not the folder itself.)
This one too if Win2K or XP.
C:\Documents and Settings\username\Local Settings\Temp\
Empty the Recycle Bin.
Reboot normally after doing the above, rescan with hijackthis, then post that log here please.