Please the BitComet Speed Guide in our official forum.
Please read BitDave's BitComet Settings Guide in our official forum.
Please read the Portforwarding guide in this wiki.
This problem only appears when you're using an older version of BitComet; it's suggested you update to the last BitComet version first. If that doesn't solve your problem, please read this topic, since the issues are most of the times related, except for that you'll have to apply all that to the BitComet.xml file. You could check also, this forum post: settings reset problem.
Please click HERE to learn how to map your ports through UPnP (UPnP enabled both in Windows and in router).
Please click HERE to learn how to map your ports in Windows firewall directly (UPnP disabled). This needs a permanent port forwarding set up in router (if any) for the same port number, as well. For details on how to do that read HERE.
You can limit the download/upload speed in Options, and there are the three ways to change rate limit.
You can also set limits for the speeds of a single task on the properties page of the task (Right-click a task and select “Properties”).