Windows 7 - Connect two PC using Remote desktop connection over the internet (DSL)

I need help.
I want to do some things on my sisters' laptop which is in other country. Here is the situation:

My computer has Windows 7 Ultimate (64 bit) installed and I am using ADSL internet connection.

My sister lives far away in UK and her lap-top is connected to internet using the wireless. Window 7 ultimate is installed at her computer too.

Since I am complete beginner, please provide me step by step tutorial. I have tried a lot of tutorials that i have found on the web, but with no success.

Thanks a lot.

Hiya pal and welcome to the forums Have a looky over here ....

Teamviewer Tutorial

Teamviewer Download
One of the best free remote programs on the market and a good tutorial on how to use it.
I live in the UK and I've remoted many a user in the US with no problems

Does this mean that this software must be installed on both computers (my PC, and the one which will be controlled remotely)?

On the company website is written that there is no need for TeamViewer to be installed on client computer.

In the tutorial you mentioned they say that client must provide me his ID & password codes... Can you describe this more please?