This is JUST MY OPINION but (and yes I read your post you said you have a 32-bit OS: so yes I know do not have a folder called "C:\Programs Files (x86)")

I'm pretty sure that is NOW a GENERIC PG warning when it's trying to load ANY VST/VSTi .DLL that is invalid, corrupt, not a audio or "music" (VST/VSTi) .dll, etc. It could be you or PG pointed BIAB to a invalid or NOT YET properly installed/configured/AUTHORIZED AmpliTube 3 .dll.

1. Neither PG or IK Multimedia actually install the actual VST plug-in (.dll) called "AmpliTube 3 .dll" in the folder called
C:\Program Files\IK Multimedia\Amplitube 3

That folder is where the User Manual and other .pdf's goes, the Amplitube 3 "standalone" executable, some files you don’t need to worry about (vpa's), etc.

2. Not sure where PG does a default install of AmpliTube 3.dll (I have full AT 3 and now AT 4 as well and don’t let PG re-install any IK stuff) so it may or MAY NOT be installed in that Steinberg folder in PG your warning, (i.e.,

C:\Program Files\Steinberg\Vstplugins\Amplitube 3.dll

Double check your system and find all occurrences of "AmplTube 3.dll" (should actually only be one and most current is dated 2/8/2013 and is 201 KB's [as reported on my system])

The 32- bit version is dated 2/8/2013 and is 201 KB's [as reported on my 64 bit NFTS win 7 system]

The 64-bit version (3.15) is dated 12/2/2011 (yes older) and is 216 KB's [as reported blah, blah..].

You only want PG to point to the 32 bit version

3. If that is where it is the correct date/size (i.e., the 32 bit version) and it is installed in the …\Steinberg folder then you probably need to get Amplitube 3 authorized? You have already done that?
If you have previously authorized it and the standalone works without complaints about authorization then I would suggest that you UNINSTALL the VST from the BIAB VST pull-in down menu ("Plugins" - > "Options -> Remove VST Plugin (from list)…"

Then re-point BIAB to the 32 bit AmpliTube 3.dll.

My experience shows that once a VST/VSTi DLL is loaded in the PG list , loading or re-loading another one with an identical name does nothing; it WILL NOT OVERWRITE the one in the pull down list until it has been removed.

Good Luck
Larry

Win10Pro,i9,64GB,2TBSSD+20TBHDDs,1080TI,BIAB'24,Scarlett18i8,Montage7,Fusion 8HD,QS8,Integra7,XV5080,QSR,SC-8850,SPLAT,FL21&others,Komp.14,IK suite&others, just a guitar player-AXE FX III &FM9T, FishmanTP, MIDIGuitar2, GK2/3'sw/GI20