Long ago when computers actually had dial up modems I used Outlook to place calls.
As I remember I had to first set up the dialing rules in Windows. This would let the modem know how to place the calls.
At the time I had the long distance service removed from my phone service. The phone company charged $10 a month whether it was used or not. Since I did very little long distance calling, I used a 2 cents a minute (as apposed to 10-12 cents) calling card. I actually had my modem calling rules set to dial the calling card and input the pin so that all Outlook had to do was make the call. The reason I used the calling card sometimes for local numbers was some people would block private numbers.With the calling card a number far away would show up on the caller ID, not my unlisted one. So, I went through this long winded tour to say; if you have a recent (less than 5 years) computer, you will need to buy a plug in USB dial up modem or install one in your desktop case. You will need a single to dual phone spliter and it should work. I haven't tried this in Windows 7, but I would imagine you have to set the dialing rules like in XP. The majority of modems have two phone holes that allow a phone connection to be connected. Connecting the modem to the improper hole will cause the modem to not work. When inspecting the back of the modem you will commonly have either text indicating what each hole is or a picture of a phone or modem. Almost always the cable coming from your wall should be connected to the 'line' or 'line in' hole or the hole that does not have a picture of the phone next to it. The other hole allows the user to connect a phone to the back of the computer to also have a phone next to the computer, this can also be used to check for a dial tone. If you have a cordless phone you don't need to plug it into the PC.