an interesting (??) challenge

I am developing a website with a potentially large user base in rural Bulgaria and would like to set up a minimum testing platform with an old Sony Vaio PCG-R505TS (bought in 2001) that came w/ Windows ME (but which was upgraded to XP Home edition (OEM Dell disk, incl. service pack 1a) in 2004; 256 MB RAM were also added at that time). This morning, I ran the System Recovery disks to restore the laptop to its original factory settings, which includes a Conexant-Ambit Softk56 Data, Fax ICH modem. The prospect of setting up a testing ground with an old computer, a notorious OS, & a slow dial-up connection was very exciting as it would likely duplicate computer conditions in rural Bulgarian villages, but I'm not having any luck getting it to work. I keep getting an error message: "The modem is not plugged in or out of service." Thinking it was a driver issue, I downloaded the updated drivers for the modem off the Sony website onto a Sandisk Cruzer flash drive, but couldn't transfer them to the Vaio, because the Vaio wouldn't recognize the flash drive... So, before I lose yet another day, can anyone please tell me if what I'm trying to do is even possible? And if so, how do I set this all up? BTW, I have Comcast high-speed cable for my main computer & a digital phone line (VOIP). One of the dial-up ISPs told me that their software would not be compatible with a digital phone line, and another was skeptical. Comcast's website, though, claims that their "Digital Voice® service permits dial-up access to Internet Service Providers", and this was confirmed by a Tech Support supervisor. Any insight and suggestions would be greatly appreciated. Many thanks.