I started with this research rather late - in 2023, original problem has been introduced with XP_SP3 release, so in 2008 - quite nasty really:
I have experimented with Diskeeper (2010, 2011, 12) and Avast filters in XP_SP3, because the way at least Avast (its filter drivers) is set up does slow down the system (its aswSP is at altitude 388401 but group is set as FSFilter Security enhancer, which is at much lower altitude range). With any program that "lies" thusly to XP_SP3 the computer gets bogged down for a nit-picking reason (IMO).
I have found out that just for the XP_SP3 M$ really messed up fltMgr driver to require a mini-filter
to really obey it's "Group"'s altitude range, which is quite a bit different than in XP_SP2 or Vista and newer Windows.
Therefore I would like to know if there is a newer fltMgr.sys driver (or a modification) that allows "normal" (not so restrictive) mini-filter behaviour (basically altitude freedom) for XP_SP3?
Example: DKRtWrt mini-filter is usually at 137100 (its native altitude as per M$'s own list) in XP_SP2 even though it's "Group" is "Activity Monitor", but can't be in XP_SP3 and its restrictive fltmgr - it's unstoppable (manually) then.
Current version is 5.1.2600.5512. I tried transplanting it with Vista's (doesn't work) and XP_SP2 (works but lacks certain functionality for Avast to work properly).
A working, perhaps temporary, solution by me was to re-classify aswSP as FSFilter Activity monitor (as was in old Avast 11 AV), add missing filter groups of virtualization and imaging to xp's GroupOrderList and ServiceOrderGroup/List (registry CurrCtrlSet) now all works well, however the nagging question remains - why should XP_SP3 be an exception - is it to further disable it in light of higher versions of the OS? I sure think so.