Not what you want to hear but I'll suggest you

might want to reach beyond the forums here and get on site help. While a generic answer can be obtained this way, step by step cannot. Who does this will need to know the OS of each to know whether or not such remote access is possible natively or if 3rd party software will be needed. XP and Win7 can offer remote access as long as both are Pro versions. Perhaps you can supply more information about the operating systems on both PCs, what type of internet service, your own expertise and capabilities, etc.