Usually problems with installing the Express PC means there's a resource conflict happening in windows. The Express PC works best on IRQ 5 and 11 (2 and 9 share the same resource chip, so they're not really different IRQs, and 2 is always taken). Go to the device manager (right click on "My computer" and choose properties). Double click on the computer icon at the top of the list. If a device is taking IRQ 5 or 11, you will need to move the device to claim another resource, so the Express PC can operate properly.

As well, you can view i/o addresses in device manager (same window as the IRQ list, just choose the i/o address radio button). No other device should be taking an i/o address range of 300, 304, 340 or 344.

If the problem is persistent, check the ISA card type. If you're running an 8 bit card (one connector to the ISA slot), it may not work with faster computers like Pentium II/III 200/500MHz machines. An upgrade to a 16 bit card may get you up and running. If you're registered, you can get a replacement 16 bit ISA card. Contact Tech support at 617-576-3066 for details on ordering a replacement ISA card.