Hello Yorkshire Lass,
Are you sure that it was a trojan? If you feel that it shouldn't have been identified there is a procedure for submission to get it cleared. I can tell you about that if you wish.
To locate the quarantined item just open Security Center by double-clicking the taskbar "M".
Click "Advanced Menu" at bottom left
Click Restore at left.
You can deal with anything that has been quarantined there. If Incredimail installed OK you can remove the item altogether, or you can restore it if you wish.