What was the infected file name (is it the installer or a file within it), what was the virus/trojan name given by avast ?
If you are happy about the use of swpr and you are sure that there is no other risk other than its perceived risk and you accept this risk then you can add it to add it to the exclusions lists Program Settings, Exclusions and the Standard Shield, Customize, Advanced and Program Settings, Exclusions.
That should allow you to install it but you might have further issues after installation so as files are unpacked and installed.
You may need to add it (the detected file/s) to the Exclusions Lists also. You may also have to add the programs executable file to the ignored processes list in the avast4.ini file, but we can look at that after you get it installed.