I use windows 8.1 on a small home LAN. Event viewer system log tells me (I think it was an warning, might have been an error) that the TDI filter is not Microsoft certified. Ignoring it does not appear to have any harmful effect, but I would like the error not to reappear. If I switch to the WFP filter, is this Microsoft certified?. I assume that SoftPerfect is using a proprietary WFP filter? How much does it cost to certify a filter with Microsoft?