It took 3 days, but I've finally finished downloading the ST3 libraries. Yay.
 
Unfortunately, every one of the zipped library files comes back "Windows cannot open this folder. The compressed folder .... is invalid" when I try to open them. I'm about to join cclarry on the IKM picket line.
 
Question: if you still have your ST3 downloaded sound (.zip) files, what size are they? Mine are between 1.3 and 1.5 GB each, 11GB total. But it's supposed to be 33GB uncompressed, and I usually don't see 66% compression ratios for audio files. That might suggest they've been truncated. But  ALL of them? Sheesh.

Give me a bit to check out files. You did make sure to unzip the first one? I thkin if you unzip the others you get that message.

Try opening and extracting zip files with Win RAR freeeie.
 
sometimes windows zip internal extractor can give errors when there really isn't anything wrong with the actual zip file.
 
you can try one of the alternative zip apps like 7zip or winzip.
 
after all the pain of downloading I would try different solutions prior to having to redownload all those files again (tho I have a fast internet connection so it's not really a problem downloading gigs of data).

Yes, the first file containing the installer unzipped OK. It's the library files that won't open.
 
I thought maybe the zip files were encrypted and that the installer would uncompress them, but that's not the case. The accompanying pdf was no help, since the instructions pertained to every other product than SampleTank. I've contacted IK Support, but if they just tell me I have to spend 3 more days re-downloading those files I am not going to be happy.
 
Thanks for helping, dub.
 

I'll be home in about an hour to test

Bit,
If this helps here are the sizes when I downloaded ST3. I had to download part 2 twice. This was the working one. 
Part Size
1     2095981
2     3241252
3     2924196
4     3143289
5     3364457
6     3540284
7     3355486
8     4192608

Ouch. That's what I was afraid of. All my files are smaller than that. Looks like they got truncated.
 
Thanks, ArcRex.

HI Bit - did you use a download manager? - when I used to have a slow download link, this use to happen all the time (here we also used to get  breaks in connection  that ALWAYS caused issues with big downloads)
I found after much trial and error  that flashget was the best - haven't used it in sometime since The Island got its internet connection better sorted, but used to be a life saver.
Nigel
 

No, I did not use a download manager. I usually do, but the one I use is a Firefox plugin and I didn't have Firefox installed on this machine yet. I do now. Started the downloads over...says it'll be done sometime Friday. Should have paid extra for the boxed product. UPS would have been quicker. Taking a boat to Italy and picking it up in person would have been quicker.

I got the discs from Sweetwater on the cheap upgrade deal  - I've only just installed it over the weekend - had some issues with the latest update (3.3 I think) and had to download that twice and install it twice - first time I installed Sonar did not scan it properly and thought it was a audio effect!!
Anyway seems to be working a little better now.
I suppose its OK, but compared to Kontakt and Mach 5, its pretty lame. 
Glad the upgrade was cheap and at least I can use my Old xpansion Tanks and SampleTron stuff.
If you have quite a lot of the expansion tanks or old stuff to load, there seems to be a bit of a knack to loading that  -took me a while to suss out but once you get the hang of taking your time, and not trying to do too many, it works OK.
One thing though - make sure you name the new libraries carefully and exactly as you want them - there does not appear to be a way to change the name or delete them - it says it has that function, but it would not work on mine - saying that haven't tried it since I upgraded about 30 minutes ago!
Nigel