Trying to install MMTTY in 'new' Win 10 computer.
Have tried V. 170 & 166. Keep getting 'set up' window showing up
on one minute intervals trying to open a new window. Until I looked
at task bar, I had several attempts.
Is this a Windows issue or MMTTY?

I just did a test.. MMTTY 170K , it installed fine on latest Windows 10..

Some more info on your computer setup could help figure out what is happening..

A couple of things to check or try.. 

- Did you get the file from https://hamsoft.ca ?
- download again the file may be corrupted
- try to install as administrator - Right click on MMTTY170K.exe then click on "Run as Administrator"
- antivirus programs can sometimes give problems  with installs

Some ideas to start with.. 

73..  Ken - VE5KChttps://hamsoft.ca