Do an ls -l on this "1" file, what does that show... What is inside the file (more 1)? Have a look at when the file was last modified (in the ls -l listing) - what were you doing then?
Where is this file? Is it in /tmp? your home directory? elsewhere?
If it keeps reappearing, it could be something your doing, or maybe a cron job is putting it there? (Check your crontab - if you're allowed to use cron, that is).
Questions, questions, questions!
Cheers
ZB