You cannot under normal circumstances have write access to the Program Files folder on OS's from Vista on up. The idea is that it reduces the incidence of virus activity, since you should not need to write there.
So you basically have two options:
1) Upgrade your application access to Admin (which will mean the user giving his permission in the same way that he has to for installations, and for the same reason)
2) Find somewhere better to extract your files. If they are data files, then they really, really shouldn't be under the Program Files folder at all - access restrictions here will only get stronger, not weaker so you will have more problems in the future, not less. For data file, consider moving them here:
Where should I store my data?[
^]