Com port
It is likely that you need to identify whether the COM port on your laptop is enabled, what COM port number it is (probably COM1) and whether it is set to used fixed settings. Then you will need to match the software to those settings or match the settings to the software requirements. If the data bits, stop bits and parity are not correct then you may not be able to download anything. D
There is nowhere within the software to actual set the settings from what I can see: I don't have one, I've just downloaded and read the manual. The manual on page 54 states that you need to use 19200 transfer (baud) rate N-8-1 (no parity, 8 data bits and 1 stop bit: a very common setting).
Obviously you'll need to be using a correctly wired cable as well.
It's been a while since I dealt with Win98, so I'm just running up a quick install into a virtual machine so I can remember how to check the COM settings...waiting...
Right.
To check your COM port settings in Windows. Right-click My Computer, select Properties, then click the Device Manager tab, click the plus sign next to Ports (COM & LPT) and finally select the COM port you want to check and click the Properties button. In the next window click the Port Settings tab to look at the port settings.
Not sure whether the software will override these or not, but it may pay (unless you use the COM port for anything else) to make sure they are the same as above, except set the Flow Control to None, since it very likely isn't used (rarely is).
Not sure if any of that will help, but might point you in the right direction.