so just the webshield that is fooling those online speedtests.
That might not be the case, it could also be that upload speeds from the MS server to my pc are not faster than
15-20Mbit/s and that at those speeds there is no problem with avast webshield.
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EDIT:
I just noticed a funny thing during all this testing.
After turning all shields off and on again 5 times the speedtests give 80Mbit/s download.
Downloading the XP SP3 file then takes 1 min 40 sec (so around 3MB/s or 24Mbit/s)
Restarted pc: back to the old results, disable/enable shields 5x: speedtests 80Mbit/s download and xp sp3 file download almost twice as fast.