Second first ... it doesn't. Only when you reinstall Windows AND you only had the font in your Windows\Fonts directory (not really great wisdom) you will loose the font.
First: Contact your font vendor, explain the situation and ask for a copy. If you can show how and when you bought it, you probably will get the copy.
If all fails: Blippo Light SF ((c) 1990-1993 Brendel Informatik & SoftMaker Software GmbH.) also came with Serif's DrawPlus X2 and PagePlus X2.
My PC crashed recently and i lost a font that looks great on the website i'm building...
I need the font - Blippo Light SF
...& how come it disappeared from microsoft windows when my PC crashed?
Thanks