Do you mean you have an XP CD, and you want to kill Win95 before you
install it? In that case, put in a startup floppy (or boot from the XP
CD, if your machine will do that) and format. Or delete the old
partition, if you want to. Of course, either of these will lose all
data on that partition, but that seems to be what you want to do.

If this is where you are, you want to make SURE that your computer
will run XP before you delete Win95! Go to www.microsoft.com and
search for the XP Upgrade advisor. That will examine your machine and
tell it whether it will be able to run XP. (If it's old enough to be
running Win95, there's a good chance that it won't handle XP.)

Or are you dual-booting XP and Win95, and want to get rid of Win95?
I'm less sure of the procedure here, but there's a file somewhere -
probably in the root of C:, but I don't know for sure - that displays
the menu that you see when you boot. If you can find that file, you
should be able to delete the Win95 option. Then you cal just delete
the Win95 directory on the disk.