Major/noticeable changes to version 2017.08.01
vDos won’t run anymore in Windows XP (it was then already somewhat crippled), it’s now “Windows 7 or later” to ease future Windows compatibility. vDos can however still be installed and used on Windows Vista.
4DOS is no longer embedded as the default command processor. Hardly anyone used the 4DOS extra functionality, while it proved to be confusing to others. The previous internal command processor is reinstated, though largely revised. As a bonus vDos.exe is 28% smaller, vDos not executing the 4DOS 16-bit code, applications start slightly faster, while free conventional memory increases 4KB.
A FPU (Floating-point unit) is added to the emulated CPU. Programs utilizing a FPU can run substantially faster.
Protected mode support and bare extended memory (XMEM-EXT) usage is overhauled.
More progressive idle detection (lowering the real CPU/core load) and responsive DOS mouse handling.
The LOW= directive in config.txt is dropped. vDos detects faulty EXEPACKed programs itself, and applies the required memory adjustments to let them run properly.
More robust and comprehensive pasting of Windows Clipboard text.
Minor printing issues resolved. Added SEL = "" option to select the default Windows printer.
Integrated WP Shell emulation to Windows Clipboard. Direct copy/append of WP’s selected text, paste text w/o the keyboard buffer roundabout and ASCII restrictions. Support of the VGA512 extended character set.
COLS/LINS directive in config.txt accepts larger maximum values, determined by the formula COLS x LINS < 16,385 (a minimal font size is of course still enforced).
[Win]+Ctrl+C copies text starting at the cursor (as long in the same fore/background color) to the end of the line. So it's now a more useful quick (to the end of) line or field copy.
Loading a DOS COM executable, a free/available 64KB memory segment was just assumed at setting the initial programs SP value.
Do you actually know what you're about to download/install? Anti-virus program complaining: Read (at least) the FAQs page: Getting started - Anti-virus program blocks vDosSetup.
Download vDos: Installation program 2017.08.01 | Source files and older versions
First read the little documentation vDos has to offer to make it run your application! Keep in mind you once had to configure DOS, the transition to Windows (XP?) took time. You forgot about that…

Have a look at the FAQs page, consult the vDos forum at SourceForge, eventually post your question/problem there. The forum is monitored by Edward Mendelson and me, replies are mostly real quick.
If your issue however seems real specific to your situation/application, or you don’t want it public: Send a mail to (change the "a" to an "o").

Submitting a problem or issue: Describe it as detailed as possible, eventually attach your autoexec and config.txt files. If your autoexec.txt starts another batch file, include that also. A mere “My DOS program won’t …” doesn’t help to come with a solution.