No, the Thomson Speedtouch ADSL (USB) modem is only suitable for ADSL.
What you need for a temporary connection to the phone line is a 56K dialup modem. These can still be obtained in a variety of flavours. If the PC has a serial port (unlikely), then a basic external modem cabled to this port should work fine. There are also 56K modems on PCMCIA cards if this is a laptop which has a suitable slot. USB dialup modems are also obtainable, but I have never actually used one myself.
Whatever you buy as a temporary measure, make sure it has drivers suitable for the operating system on that PC.
ROGER - G0AOZ.