Hello,
I came here to report this incompatibility.
After I had successfully installed PLSQL developer 7.1.0 on a Windows NT 4.0 (with SP6a+), I tried to start it.
Then I discovered a typical GUI incompatibility (which happens with a lot of newer programs). The incompatibility is that a program is using some GUI functions which are present only in Windows 2000 and XP. I consider this to be a completely unnecessary restriction, since those aren't games so that they'd need fancy GUI effects (and if they were, they'd be using DirectX).
This is what happened:
During startup, I encountered a fatal error about missing MSIMG32.DLL:

Then I transferred this file from a Windows 2000 PC (it was in \WINNT\System32\) into my \WINNT\System32\, and started the program again. This time I got another error (which I expected to happen from my experience with other programs which had the same incompatibility):

This situation is unresolvable "from the client side" as far as I know. A developer has to clense his code of newer API calls (specific to Windows 2K/XP) to remedy this issue.
Please do that and retain your program's compatibility with NT 4.0. By the way, PLSQL Developer v6.0 works just fine with Windows NT 4.0.
I came here to report this incompatibility.
After I had successfully installed PLSQL developer 7.1.0 on a Windows NT 4.0 (with SP6a+), I tried to start it.
Then I discovered a typical GUI incompatibility (which happens with a lot of newer programs). The incompatibility is that a program is using some GUI functions which are present only in Windows 2000 and XP. I consider this to be a completely unnecessary restriction, since those aren't games so that they'd need fancy GUI effects (and if they were, they'd be using DirectX).
This is what happened:
During startup, I encountered a fatal error about missing MSIMG32.DLL:

Then I transferred this file from a Windows 2000 PC (it was in \WINNT\System32\) into my \WINNT\System32\, and started the program again. This time I got another error (which I expected to happen from my experience with other programs which had the same incompatibility):

This situation is unresolvable "from the client side" as far as I know. A developer has to clense his code of newer API calls (specific to Windows 2K/XP) to remedy this issue.
Please do that and retain your program's compatibility with NT 4.0. By the way, PLSQL Developer v6.0 works just fine with Windows NT 4.0.