multiple indices over 1 field

I have inherited the responsibility for a server that has a front-end
database (does the AM/PM processing) and most of the tables are in
separate back-end DB's.

In trying to clean up the system (and speed up the processing) I have
found that many of the B/E DB's have multiple indices over the same
field.
Example:
Field IndexName
OrdNo OrdNo
OrdNo PrimaryKey
OrdNo Index_OrdNo
OrdNo OrderheaderOrdNo

Now I am an Access newbie (but have many years of DB experience on
other systems), I have a few questions.
1. Is there any reason why we would need the extra indices?
2. I can not seem to find them referenced in any queries/forms/reports/
macros or modules. Is there any way to identify if they are being
used?
3. There are multiple users that have their own DB's that have links
to the backend DB's. Short of checking each of the users DB's how can
I find out if they are being referenced by another DB?
4. What kind of problems will I be facing if I just go ahead and
delete them?

The machine is running Win2K using A2003.

Thanks in advance for any help/suggestions.
-pb
.