When I download a file ClamWin ALWAYS scans the download -- even if it is from a source that I know is virus-free. This slows my computer so much that I can do nothing else until the scan is complete. Is it possible to disable this behavior?

ClamWin does not scan files in real-time when they are downloaded. ClamWin is an on-demand scanner--meaning it only scans files when you "demand" it to via the Windows Explorer right-click menu or when you have scheduled a scan.

Clam Sentinel is a separate little program that you can use with ClamWin to scan in real-time as files are added, modified, or copied to your computer.

So if you are not using Clam Sentinel with ClamWin, something else must be scanning your downloaded files, and we can't help with that.

You can excluded files from ClamWin's on-demand scans via the configuration menu--filters, exclude matching filenames. You can exclude files from Clam Sentinel's real-time scans via the advanced settings, paths or files not scanned.

Regards,

Most browsers scan the files on download, but only the download origin is scanned against known phishing/malware sites.