Solution
Verify if any instance of these components is installed. Open Add or Remove Programs and look for these entries
OPNET AppTransaction Xpert
OPNET License Server
OPNET AppTransaction Xpert Documentation
If none of the previous entries is in the Add and Remove Programs dialog, but Transaction Analyzer installer keeps showing the warning that user has to remove the OPNET products, verify the following keys are not in the Windows Registry:
HKLM > SOFTWARE > Wow6432Node > OPNET Technologies > OPNET > [OLD VERSION]
HKLM > SOFTWARE > Wow6432Node > OPNET Technologies > AppTransaction Xpert [OLD VERSION]
HKLM > SOFTWARE > Wow6432Node > OPNET Technologies > AppTransaction License Server [OLD VERSION]
HKLM > SOFTWARE > Wow6432Node > OPNET Technologies > AppTransaction Xpert Documentation [OLD VERSION]
It would be also useful to take a look at the installer log files that are automatically generated when executing the TA 17.5 installer wizard. The files can be retrieved from this folder:
[USER_ACCOUNT]\AppData\Local\Temp
And they should be named:
SteelCentral_Transaction_Analyzer_[TIMESTAMP]
SteelCentral_Transaction_Analyzer_[TIMESTAMP]_[INDEX]_SteelCentralTransactionAnalyzer.msi.log
SteelCentral_Transaction_Analyzer_[TIMESTAMP]_[INDEX]_SteelCentralTransactionAnalyzerLicense.msi.log