So what is my modem?
A name brand will have full instructions and customer support. Many modems are "unbranded" or carry the dealer's name rather than the manufacturer. These usually give perfectly good performance at a budget price. Often they will be found to be Rockwell based. Even if it is an internal modem, there is no need to see the modem to find out. Offline, go to Start-Settings-Control Panel-Modems. Click on the Diagnostics tab, select the modem from the list presented, then click on More Info... ATI3 and ATI6 give the clues. RCVxxxx... in ATI6 will tell you if you have Rockwell chips, or another manufacturer code. ATI3 tells you the version of the code. However you will need to find out the actual manufacturer if you need a firmware (flash) upgrade. The retailer may be able to tell you. In some cases ATI4 will give a clue.

For US-spec modems: Every computer part which emits RF (video card, motherboard, hard drive, modem, well you get the picture) should have a FCC ID:number on the card. Go to this site and enter the FCC ID number and it will tell you who and when it was made. This site has every ID from the FCC from 1987 to the present. You can get this same info from the FCC site but it is not as user friendly. SBSdirect (FCC id site) link temporarily removed as SBS have disappeared without trace, leaving a lawsuit behind...
If there is no FCC number, the model number can often give a clue. Two common ones are FM-56xx, made by Well and 1456VQx, made by Askey (USA) or Askey (elsewhere) A lot of "unbranded" modems are made by these two. Askey are also known as Dynalink.