Ok..You are using a DG41 chipset...Unclear manual and support?...and you saying "bios is not having these features to assign PCI slots and IRQs" //....Perhaps is telling you it does not support it in bios.
But...if you reduce the IRQ's being used to some but not all...You might gain to move one to be free, if you free up some....how to, is remove, disable, and tweak or test....only you can, if using and having it before you to try to do.
IDE on board?
SATA 1 or 2?
This is why the G41 is added a D? DG41...both old having some, IDE, floppy support?... and newer SATA ports added, were added as new, with usb updates also to usb2?..and you adding in more cards of usb...and another card of firewire...what about video?...onboard and or slotted type?....So, as you see, keyboard and mouse also...serial and coms...nic and or wi fi....all take up what is left over...and are hard wired some to....if no switch is put in bios control...how does one turn it off or disable the call for services start up on boot for the use there of, not not be used...MS config is the answer?....
So, here is where you might find it hard to move anything, or disable ...they filled it already with the sata addition...and usb...also...and ide...and most likely a video chip....doesn't leave much wiggle room eh?.
So...as some and I have said...it ain't easy..even if you get it to do it...it will still cause issues!...Right?...and you have them...surely trying...then, if you try all...the wall will come down one way or another.....And you will see.
I think some assignment was set as...IDE 1 and 2/ Floppy drives...were set to a specific IRQ...if you free them up...you might gain the use of...But then again...the OS might reserve those for , as storage device lanes or such services set for if detected to run on and with....if you cannot defeat them in Bios.
You might try to use the device manager, but some issues may arise using ...is to try and see if you can, turn off what is not necessary first!...if not doing, all irqs being used, will only result in sharing states!...it does not support the OS XP...features XP had to offer in allowing irq management...or you are not freeing up any?....is the only solution I see being ...The wall you made...and saying this is not able to be done...but you might be overlooking how to first free them up...then they can be used....is not always so!..it depends on how they are disabled sometimes...so that the OS does not detect them, when being installed as first time os put... and thus the OS sees first and puts in the services for...and install the base services for what you say cannot be disabled in bios..ties it to services....If you install the os with these things enabled, the installation of the OS will put services on for them, and boot them up when booting...So, you may have to end some services to manual modes...Hence Tweaking or hacking them also...might be something to think about....And or, a setup of Bios first, then install the OS...stops the os from putting holds on irq management and shared states...and or placement holders for!
Now some of this stuff can be disabled..ide, and usb, com, serial and or other features in bios or not?...then try it out...you will get one or the other...that removes one from the sharing of..what you want not shared....Right?.
If it does not let you, is because the irqs are full and or over fully used!...and the ones the OS will not share, are being used, you might have over looked can be disabled, some how, some way...or not.
If you say not....then?...should I argue?