I've just recovered from exactly this problem - again after installing
audio software. In this case I think it was Waves software which also
installed something called TPkd - which I think is something made by a
company called Pace to combat piracy.
Unfortunately this installs something which XP sees as a non-Plug and
Play device - which hogs IRQ6, knocking out your floppy disk drive.
To eliminate this I had to do a number of things. First of all go to
Device Manager (right click My Computer, select
Properties/Hardware/Device Manager). Now select View/Show Hidden
Devices. This adds "Non-Plug and Play drivers" to this list. In here
you should find TPkd, which must be uninstalled (select from right
click menu).
Then you need to delete anything associated with this in the system.
To be absolutely sure, I did a file search for tpkd* - which in my
case found five files, including two each of .sys and tpkdboot and one
vxd. These went straight into the recycle bin.
Finally I took a look in the tpkdboot files and found the registry
instructions which they had added to my system. Being reckless I
didn't make a back-up of the registry first, but I'd advise it! Then I
went to the following folder:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TPkd]
This seems to hold all the TPkd information, and I deleted it at this
level - no more TPkd of any description in the registry.
Finally I rebooted and after a couple of tries (I'd not done all this
together, but by trial and error got here) everything now runs
smoothly again.
I've written this out in detail because your problem sounds absolutely
identical to mine. After reading around the net I found many other
problems of a similar nature, and maybe this would solve some of those
too - but let me know if this is helpful to you!