I have two hard drives: a 10GB internal hard drive and an 80GB USB
external drive. There are certain folders on the internal drive which
I would like to have automatically copied over to the external drive
every night, to serve as a backup. I'm running Windows 2000. Is there
any way to do this?

The easiest way would to schedule a daily backup using Microsoft's
included backup utility named aptly, Backup. You can schedule a
nightly job and have it save the backup file onto your external
harddrive, and it will give you options to of what time to schedule
the backup, whether or not you want to compress it or not, etc. Play
around in the options and I'm sure you'll find what you're looking
for. In order to launch backup, go into your Start
Menu-->Programs-->Accessories-->System Tools-->Backup. If it's not
there, then stick in your Win2k install cd, and add that component,
it's very nice. Thanks for your question!

skermit-ga

Good for you - performing backups!  Most PC users do not understand
that everything can disappear forever in an instant.  Could I ever
tell you some stories of people that have lost everything.  Then,
think that I should magically be able get it back for them when they
have never made a backup.  I had a phone call once that started out "I
am going to commit suicide ... you have to get it working again ...".

I do two things:

1> Daily: I backup my data automatically with Second Copy.

2> Before any major changes: I make an image of my hard drive with
Ghost. I do this just before I install any new programs.  Then, if
anything goes wrong I have the ultimate un-do by simply restoring the
complete hard drive.

http://www.secondcopy.com
It is a shareware program which is fully operational for 30 days. 
Then, if you like it there is a small fee.  Check it out.
I really like the simplicity of this program.  And, there is a nifty
feature to have it keep old versions of a data file - they are marked
as "2nd last version of ... ", etc.

http://www.symantec.com/sabu/ghost/ghost_personal/
Ghost from Norton makes perfect copies of your hard drive.  It is
available individually or in the Norton System Works Professional
package.  I use Ghost and the Anti-Virus from the package and do not
install all the other items.

Whatever you do ... be able to test your backups.  I have seen too
many backup programs seem to work then when it comes time to perform a
restore all hell breaks loose.