Need help with query

PHP and SQL

Hello all.  I am hoping for some help in determining the needed SQL and best way to create a resulting html SELECT input.

Details:

- I need to create an html select that contains a treelike category structure.
- I only want the categories to be in the select if there are files with the category id
- I want the select to demonstrate the level. For example:
Cat 1
  Sub Cat 1
    Sub Sub Cat 1
  Sub Cat 2
Cat 2

Here are the details on the tables/fields
tblCategory
  CategoryID (int pk)
  CategoryName (varchar)
  TopLevelFlag (tinyint)
  ParentCategoryID (int)

tblFileCategory
  FileID
  CategoryID

Additional Notes:
Some categories do not directly have files associated. For example
Living Accomodations
  Home
    Small
      [Small contains 1 file]
    Large
  Apartment
    [Apartment contains 5 files]
  Condo

Please help me come up with the sql and method that creates the options for the select. It will be fun :).  I will award points quickly. I have to have this completed by tomorrow night.  Thanks EE!

Best,
kerkor