Vlk, it's most probably not a compatability prob.
When I was running WIN XP Pro, this happened quite often after software installations, it is, as I posted above, a kind of timing problem in the WIN startup sequence and discussed in many forums.
Many "solutions" to this behaviour have been posted throughout the web, but to my knowledge none of them work for every machine, thus there is no panacea to cure it.
I just ignored it.
Sometimes this worked for me: went to sys control, sound options and turned off the volume control task bar icon. Rebooted. All icons appeared (miraculously). Then turned on again the volume control icon. Rebooted. Everything fine.
As said: worked only sometimes. Sometimes the behaviour cured itself after any windows update...
Again, the missing of icons does not effect the actual services: everything is working as it should.
Thx
Zyndstoff