I assume by identities you mean you wish to create new users. Open Control
Panel, open User Accounts, click "Create a new account" and follow the
screen. Note, if these accounts are to be password protected, when you
finish creating the account, in the left frame there should be a link about
protecting your computer from lost passwords, use that and follow the
instructions for creating a password reset disk.
As to the access issue, you will need to use the Group Profile Editor:
http://support.microsoft.com/default.aspx?scid=kb;en-us;307882
Note, the Group Profile Editor is only available in XP Pro and is not
available in XP Home Edition. In addition to the information above with
regard to setting user access, you might want to post this question to the
windowsxp.configuration_manage newsgroup as they may be able to give you
specific instructions beyond the general use of the Group Policy Editor
article to which I've provided a link above.
Also note, many applications were not created for a multi-user environment
and the GPE notwithstanding, you may need to do the following to give access
to more than one user:
First, be sure the account to which you wish to grant access is set to
administrator and not limited. Install the applications to the same folder
in which it was originally installed. This will look the same as one
install on your hard drive but create the pointers necessary for this user
to have access to the application.
Once the installation is complete, you can return the account to its limited
status if that is what you want and the user should still have access.