Traditionally motherboards were built with 2 on board IDE ports. However more and more mother board's are coming with 1 due to the use of SATA ports. The one IDE port i usually used for the CD-ROM.
It depends on how many ports are on the hub. Some might have 4 ports, some might have 8 ports some might have 16 ports etc...
usb 2.0 can support 127 devices
A router will typically support between 4 and 8 ports. For additional ports, a standard Ethernet switch can be connected to one of the ports.
serial ports are not in use any more, the new standard is usb
Generally speaking, only one. However, there are some devices, known as "port multipliers" that will allow you to connect up to 15 devices to a single channel.
Many different mother boards have been made to accomidate the latest microprocessors. I would say there have been 32 different mother board designs for handling the slot numbers of the processors.
Windows xp will support 127 usb ports
Full AT, Baby AT, and ATX
24-pin
There's no possible answer to that. A computer can have any number of USB ports. As the above is true, it doesn't matter how many you use. You can use as much USB ports as you want on your computer.
In regards to the average usb port hub and how many ports are available, this can vary. The average usb port hub can support up to four usb inputs at a time.