Wow... Umm..
To be honest... Looking at your system specs, you're not likely to find a software option that will run well enough to give you many practical options. But if you were to get the remote party online then you could use several programs to run VOIP but it won't be dialing into a land line. For example... It's been a long time but if Buddy Phone is still around then that's an excellent option. I was able to use that between two 56K modems without any problems. Ran smoothly in fact.
Anymore we tend to use software such as Netmeeting or the VOIP capabilities of chat mediums such as Yahoo. (But I'm sure you've already known about these.)
There's always that one program that's been advertised for forever and a day... Net2Phone. (
http://www.net2phone.com/ ) But it's a pay service and seems overly-complicated to be honest.
You can always go look in the major electronics stores in their peripherials or software sections for ideas. I know that there's lots of hardware out there that you can buy to pretty much do what you're wanting to do. Some of them look like some viable options for you. I've never really paid an extended amount of attention to these things. But I've looked at them enough to know that they're a pretty solid option worth looking at. Beware though.. Half of them (if not MOST...) require that you set up a paid account first.
Other than that...you don't really have many options unless you've got a lot of friends in the corporate sector. (Such as my own previous employer...Lucent Technologies. I did Data/VOIP/DSL with them.) They have A LOT of technology and software that the public doesn't know about...and it works GREAT. I never understood why they don't just release it to the public sector...
Hope this helps.