OK, so I have had the original BAT installed and working great for some time now but I had it installed in "C:\Program Files (x86)\Steam\steamapps\common\IL 2 Sturmovik 1946". It worked fine so I never had any cause to read up and find out that I should have installed outside of Program Files. Well, I live in the sticks and my Verizon Wi-Fi is about as fast and reliable as 1990s dial-up so I only got the chance to download the expansions this past weekend when I visited some relatives who live in civilization. I created a folder "C:\BATUPDATESANDMODS" with subfolders "Checkpoint Charlie", "Sealion", "Angels High", "Pathfinder", and "Pathfinder Evolution" and directed all the zip file downloads and installers to their respective folders. When I clicked on the installer for Checkpoint Charlie I tried to install it in "C:\Program Files (x86)\Steam\steamapps\common\IL 2 Sturmovik 1946" and got an instant install error. So I came here and read up on how you shouldn't have BAT installed under program files leading me to copy my entire "IL-2 Sturmovik 1946" file out of the Steam folder and paste it directly into C. I then tried to install Checkpoint Charlie to location "C:\IL 2 Sturmovik 1946" and this is the install error log I receive.
Checking File CHECKPOINT_CHARLIE_01.ZIP
CHECKPOINT_CHARLIE_01.ZIP is damaged!
Checksum should be: ed44fa4f
Checksum is : 2CDF47A8
Checking File CHECKPOINT_CHARLIE_02.ZIP
CHECKPOINT_CHARLIE_02.ZIP is damaged!
Checksum should be: 730d46a9
Checksum is : 03B53B3B
Checking File CHECKPOINT_CHARLIE_03.ZIP
CHECKPOINT_CHARLIE_03.ZIP is damaged!
Checksum should be: ba4b3d2c
Checksum is : 1B7D888C
Checking File CHECKPOINT_CHARLIE_04.ZIP
CHECKPOINT_CHARLIE_04.ZIP is damaged!
Checksum should be: ad6a7c43
Checksum is : 69ECBBE7
Checking File CHECKPOINT_CHARLIE_05.ZIP
CHECKPOINT_CHARLIE_05.ZIP is damaged!
Checksum should be: 7afcca30
Checksum is : 22E69BCC
Checking File CHECKPOINT_CHARLIE_06.ZIP
CHECKPOINT_CHARLIE_06.ZIP is damaged!
Checksum should be: 791d59db
Checksum is : DB44CB2E
Checking File CHECKPOINT_CHARLIE_07.ZIP
CHECKPOINT_CHARLIE_07.ZIP is damaged!
Checksum should be: 60168e1d
Checksum is : C1208D6D
Errors occured, aborting installation!
Creating Installer Logfile
I am 99% sure that, as usual, I have done something grievously wrong and that the fix will be something that will leave me hanging my head in shame at my computer illiteracy and density but any help will be much appreciated!