While most antiviruses should remove the regitry key entries, information about this virus informs that only registry entry is not vitual for removal.
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\Run\Supernova=C:\WINDOWS\BLAARGH.exe
If you get an error on loading windows that it can't find the Supernova file, then look into the registry to remove it. Make a backup (export) of the registry and then delete this entry. If you screw up something, restore the backup (import) and try again....

Add: If it's Windows ME or XP that you are running, disable System Restore to make sure Windows doesn't restore the virus.

Disabling System Restore

Windows ME and XP utilize a restore utility that backs up selected files automatically to the C:\_Restore folder. This means that an infected file could be stored there as a backup file, and VirusScan will be unable to delete these files. You must disable the System Restore Utility to remove the infected files from the C:\_Restore folder.

WindowsME

1. Right click the My Computer icon on the Desktop and click on Properties.
2. Click on the Performance tab.
3. Click on the File System button.
4. Click on the Troubleshooting tab.
5. Put a check mark next to 'Disable System Restore'.
6. Click the 'OK' button.
7. You will be prompted to restart the computer. Click Yes.

Note: To re-enable the Restore Utility, follow steps one to seven and on step five remove the check mark next to 'Disable System Restore'.

WindowsXP

Disabling the System Restore Utility (Windows XP Users)

1. Right click the My Computer icon on the Desktop and click on Properties.
2. Click on the System Restore tab.
3. Put a check mark next to 'Turn off System Restore on All Drives'.
4. Click the 'OK' button.
5. You will be prompted to restart the computer. Click Yes.

Note: To re-enable the Restore Utility, follow steps one to five and on step three remove the check mark next to 'Turn off System Restore on All Drives'.

source: McAfee