I mounted a drive that was plugged in via usb so that I could format it. Then I unplugged it and now it looks for it when I boot up and it says:

"no such file or directory when trying to open /dev/sda1
Failed to check file system."

So now I can't boot up.

If you can't boot all the way, could you at least type the line with /dev/sda1 in it for us to read. It is the first place I want to look.

Check if there is an entry for /dev/sda1 in your /etc/fstab file. If so, and it was entered manually, then you need to boot up into the rescue system and comment out the line.

By entered manually, I mean it starts like '/dev/sda1 /<mountpoint> vfat'

If it looks like:
'usbfs /proc/bus/usb usbfs noauto 0 0
'
then the problem is elsewhere. Another option if the first case is true is to use the 'noauto' option, so an attempt isn't made to mount it during the boot process. This way, after inserting it, you can manually mount it (assuming the hotplug system doesn't mount it for you)

You're right!

I removed the line from fstab and it works!!!

Thanks so freaking much!