keggler

hi, was doing quite well slipstreaming vista sp1 into a vista basic cd, but the final iso burn stalled, so i killed the task and restarted - now the slipstream option isn't there? tried clearing the temp folder, re-booting... no good - strange thing is if i try to select another vista edition at the start (i know this will fail eventually), the slipstream option is there? so i can only try a slipstream once per system, then if it fails, i'm screwed? any ideas? thanks in advance