I was able to take a look at your database, and I have some general recommendations.
1. It is best not to use spaces or special characters (#,!,&,*) in your table or field names (you have some field names that have spaces)
2. It is best to have an autonumber primary key field in every table. The primary key uniquely identifies the record. You have that with the exception of the rental table.
3. Information in 1 table should not be repeated in another table with the exception of a foreign key field.
Looking at your database, your customer table looks OK with the exception of the spaces in the fieldnames, so you should take care of that.
In your media table, again remove the spaces in your field names. The other issue I see is with the media type field. If you look at your data, you repeat the same media type many times. This describes a one-to-many relationship: 1 media type to several media items. It would be better to put the media types in a separate table (1 record for each unique type) and then reference the key field in your media table.
So a table to hold the media types
tblMediaTypes
-pkMediaTypeID primary key, autonumber
-txtMediaType
From what I see you would have the following 4 records in the media type table:
pkMediaTypeID|txtMediaType
1|DVD
2|Blue Ray DVD
3|Game
4|VHS
Now you need to adjust your media table to reference the key field of the type table you just created. When you reference the primary key of 1 table in another, related table, we call the field a foreign key field. Since the autonumber datatype is just an incrementing long number integer field, the foreign key field must also be a long number integer field but it cannot be autonumber (you can have only 1 autonumber field in a table, and I would reserve that for the primary key of the table).
So we need to adjust the media table
Media
-MediaID primary key, autonumber
-MediaName (text field)
-fkMediaTypeID foreign key to tblMediaTypes, must be a long number integer datatype as explained above
-Description
Now, the main problem with your database is with the Rentals table. Here is some guidance on correcting the table (I do not want to do it for you since it is an assignment after all)
1. You need an primary key, autonumber field that uniquely identifies the rental (independent of the customer or media)
2. Do not have fields that contain information that is already in another table with the exception of the foreign key fields like I showed above.
3. no spaces or special characters in your table or field names
Now the key to setting up the rental table correctly depends on what your relationships are. Here are some questions to ask yourself?
1. Can a customer rent many media items?
2. Can a media item be rented by many customers over time?