Thanks. Have now followed these instructions. However, the problem seems exactly the same. With the parallel printer attached, once you shut down for a few hours the serial ports are replaced by 'unknown devices' when you re-boot. These are the new IRQ settings - hope they are a bit prettier. :)

0 System timer
1 Standard 101/102-Key or Microsoft Natural Keyboard
2 Programmable interrupt controller
3 Communications Port (COM2)
4 Communications Port (COM1)
5 Creative SB Live!
5 ACPI IRQ Holder for PCI IRQ Steering
6 Standard Floppy Disk Controller
7 Conexant PCI Modem Enumerator
7 Intel 82371AB/EB PCI to USB Universal Host Controller
7 ACPI IRQ Holder for PCI IRQ Steering
8 System CMOS/real time clock
9 SCI IRQ used by ACPI bus
10 D-Link DFE-530TX PCI Fast Ethernet Adapter (Rev A)
10 Matrox Millennium G400 DualHead MAX - English
10 ACPI IRQ Holder for PCI IRQ Steering
11 Highpoint Technology Inc. HPT366 Ultra DMA 66 Controller
11 Highpoint Technology Inc. HPT366 Ultra DMA 66 Controller
11 Linksys LNE100TX Fast Ethernet Adapter
11 ACPI IRQ Holder for PCI IRQ Steering
12 Cordless7 (PS/2)
13 Numeric data processor
14 Primary IDE controller (dual fifo)
14 Intel 82371AB/EB PCI Bus Master IDE Controller
15 Secondary IDE controller (dual fifo)
15 Intel 82371AB/EB PCI Bus Master IDE Controller

: Ugly - really ugly. :(

: Try these steps first and then let me know:

: 1. Note the devices that are sharing the IRQ with the USB host controller. Look in System Information > Hardware resources > IRQs.
: 2. Boot to BIOS setup (press Del, F1, or F10 at initial boot).
: 3. Go to the "Integrated Peripherals" section and disable one or both serial (Com) ports if you are not using them. Disable the LPT port if you use a USB printer.
: 4. Go to the "PnP/PCI" section and enable "PnP OS", "Auto" and "Reset Configuration Data". The last is a momentary switch and will be disabled each time you return here. It releases the BIOS lock on IRQs and lets Windows take over and is VERY important.
: 5. Boot DIRECTLY to Windows Safe Mode (continue booting and press F8 repeatedly to get the boot menu) and unplug any USB devices. Remove all USB software in Add/Remove Programs. Open Device Manager. Remove the USB root hub and host controller *in that order*. Remove all USB drivers. Look for duplicate or erroneous drivers and *remove them all*. Windows will reinstall genuine devices.
: 6. If you have any SB16 emulation drivers, disable them in the hardware profile (do not remove). These are DOS sound drivers and most don't need them.
: 7. Lastly, remove the drivers for the devices sharing the IRQ with the host controller. Windows should reinstall the drivers automatically.

: At this point you have freed up 2 or 3 IRQs and reset Windows IRQ assignments. You can reboot and reinstall your devices *as per manufacturer's instructions*.

: Bill

: : 0 System timer
: : 1 Standard 101/102-Key or Microsoft Natural Keyboard
: : 2 Programmable interrupt controller
: : 3 Communications Port (COM2)
: : 4 Communications Port (COM1)
: : 5 Creative SB16 Emulation
: : 6 Standard Floppy Disk Controller
: : 7 Printer Port (LPT1)
: : 8 System CMOS/real time clock
: : 9 SCI IRQ used by ACPI bus
: : 10 D-Link DFE-530TX PCI Fast Ethernet Adapter (Rev A)
: : 10 Creative SB Live!
: : 10 Conexant PCI Modem Enumerator
: : 10 Intel 82371AB/EB PCI to USB Universal Host Controller
: : 10 Matrox Millennium G400 DualHead MAX - English
: : 10 ACPI IRQ Holder for PCI IRQ Steering
: : 10 ACPI IRQ Holder for PCI IRQ Steering
: : 10 ACPI IRQ Holder for PCI IRQ Steering
: : 11 Highpoint Technology Inc. HPT366 Ultra DMA 66 Controller
: : 11 Highpoint Technology Inc. HPT366 Ultra DMA 66 Controller
: : 11 Linksys LNE100TX Fast Ethernet Adapter
: : 11 ACPI IRQ Holder for PCI IRQ Steering
: : 12 Cordless7 (PS/2)
: : 13 Numeric data processor
: : 14 Primary IDE controller (dual fifo)
: : 14 Intel 82371AB/EB PCI Bus Master IDE Controller
: : 15 Secondary IDE controller (dual fifo)
: : 15 Intel 82371AB/EB PCI Bus Master IDE Controller

: :
: : :
: : : Open System Information (MSINFO32.EXE) and navigate to Hardware Resources > IRQs. Click anywhere in the right pane and then press CTRL-A and then CTRL-C. You have copied that data to the clipboard. Paste that data in a reply here.

: : :
: : : : I have Windows 98 (4.10.1998) & Intel 82371AB/EB PCI to USB Universal Host Controller. I have added a Belkin USB Multi-Port Hub F5U116. The hub installs fine. The Serial Ports and USB Ports are not a problem. The Parallel Port adapter drivers (F5U002) are loaded OK and evrything is fine in the Device Manager.

: : : : When I attach my HP DeskJet 880c to the hub's parallel port I can print. I can reboot and it will still be OK. I can even Shut Down and all is well when I boot up again.

: : : : If I leave it for a while (half hour or more)and then boot up two 'Unknown Devices' are installed under USB, the Serial to USB COnvertors disappear from Device Manager and the COM ports added also vanish.

: : : : If I follow this procedure everything starts working again, although the parallel printer is then not connected:

: : : : remove the parallel cable, unplug the USB cable from the hub, reboot in SAFE mode, remove the 'Unknown Devices' from Device Manager, (the serial convertors and COM Ports are visible again in SAFE mode!), reboot in normal mode and then plug the USB cable back into the hub.

: : : : I have reinstalled the Printer Drivers, upgraded the BIOS and followed the rest of the problem solver but to no avail. Any ideas?