Hi

with you router you can try exploring different options of doing a vpn onto your lan.

You can make use of PPTP/MPPE without any additional stuffs at the client side and with the normal microsoft OS.

You can refer the below link to have some idea on the same..

http://www.cisco.com/en/US/tech/tk827/tk369/technologies_configuration_example09186a00801e51e2.shtml

The second option would be going in for vpn clients at your client sid and establishing end to end ipsec tunnel.

below link talks about the same.

http://www.cisco.com/en/US/tech/tk583/tk372/tech_configuration_examples_list.html#anchor16

On both the scenarios you need to have proper ios loaded on your router to support the required features.

regds