I've had weird problems using my Q10 on Win98SE that sound similar to yours. I tried everything I could think of for months, and nothing really took care of the problem. Usually, I can let the program run a while and then restart and the crackles disappear, so I just live with it. Annoying, but still functional.
Do you have another sound card (like a Soundblaster)?, If so, this has been shown to sometimes create problems for others. I'd try disabling any other sound cards in BIOS and in Windows and see if the problem presisits.
You could also try reinstalling your OS, and/or the sound card drivers. Do you know a program called Ghost? It is a way to make exact copies of your hard drive to CDs or to a different hard drive, and it comes in really handy for troubleshooting. When I was fiddling a lot I reformatted my hard drive, then installed Windows, then backed up my drive using Ghost before adding any other progarms or drivers. That way I could easily go back to a "virgin" Windows system and try something else without having to reinstall Windows each time.
I hope to updgrade to XP this weekend, and I really hope this takes care of my problem. I'll let you know how it goes.