Hi
Svchost.exe taking 100% CPU is often related to Windows update service. Please see if this set of instructions helps.
Let's try a little batch to get ComboFix uninstalled.
Create & execute batch file
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Open notepad and then copy and paste the bolded lines below into it. Go to File > save as and name the file UninstallCombo.bat, change the Save as type to all files and save it to your desktop. (If you are still unsure on how to do this there is a little tutorial with pictures here)
@echo off
c:
cd\Documents and Settings\aule1\Desktop
ComboFix.exe /u
Double-click on UninstallCombo.bat file to execute it.