You can edit the boot.ini to remove the first OS:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q289022
But you may want to consider backing up all your files onto CD-Rs and do a clean install.
Win XP Pro.
In order to recover from the BLAST virus I reinstalled windows on D: (original on C
.
I am now left with a screen at atart up, offering me two operating systems (both XP), the first is automaticaly chosen by time delay.
1/ How can I get rid of the unwanted O.S. and all the rubish that is probably still lingering with it.
2/ How do I then get rid of the start up selection screen?
Thanks in advance for any help.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic