Siphonblaster

How can i uninstall Combofix, if i've already manually deleted the Combofix.exe file & the subsequent C-drive folder with it? I know this certain 'USB' A-drive still exists in my computer & my clock speed hasnt reverted back to normal??? When i type in ComboFix /u, it says that it can't read a Combofix file, since i've manually deleted it...