The latest version of mIRC, v7.19, does not include OpenCandy or any other additions. If you are seeing a trojan/virus warning, this probably indicates that your anti-virus software is incorrectly thinking that the installer has a trojan/virus when it does not. This is called a false-positive and the only way to resolve the issue would be to contact your anti-virus software vendor to report the issue.
If you suspect that your anti-virus software is not working correctly, you can visit a site like Virus Total
which checks an uploaded file with all of the major anti-virus applications. If only one or two, out of around forty, report a trojan/virus, that usually indicates a false-positive.
In addition, you should not use mIRC v6.34. mIRC v6.35 was specifically released to fix a security issue in mIRC v6.34 and earlier versions, as indicated on the Latest News
page. It is rarely a good idea to use any version of mIRC other than the latest version as it always includes the latest security and bug fixes. If you use an older version of mIRC, you are leaving yourself open to exploits.