If Sirefef was found on your computer, your interests are well served by running tools that query/diagnose the system prior to Windows starting.
Although some programs may come up clean, malware could still be lurking somewhere, particularly if it is a Rootkit.
So, if you agree, let’s take a look before Windows starts, but, need some info from you:
Do you have the Repair your computer option in the Advanced Boot Options menu?
To find out:
Restart the computer.
As soon as the BIOS is loaded begin tapping the F8 key until the Advanced Boot Options menu appears.
Is the Repair your computer option listed?
If you do not have the option, do you have your Windows installation CD/DVD available?
And last, do you have a USB flash drive available, and access to a clean computer?