Our Answer:

If you set up frequently, hourly and daily it will make activeCollab happy! (The new Incoming Mail module uses frequently job to pull emails).

For Reports, once a week is sufficient, but you will need to ensure it gets called on the day your week starts (as per aC configuration you have). Webcron.org may be in some other timezone than your server. So you will need to ensure it gets fired at correct time. When cron gets executed, it checks if this is the start of the week, if so, it will take reporting snapshots.

Every week, on start of week (e.g. Monday) we take snapshot of previous week.

If your server has a web based control panel (cPanel, Plesk etc), there are good chances you can configure cron jobs with it. If you have shell access to the server (SSH), you can easily configure cron jobs from command line (crontab -e).

If all that fails, what are my alternatives?

Alright, so life is really making it difficult for you, you have two alternatives.

1. Re-install Reports module every week. When Reports module installs, it collects all historical data about your projects. Re-installing it (uninstall, and then install) will refresh your data.
2. Run cron from another computer. Either set it up on your desktop or use a third party service to run scheduled tasks (e.g. Webcron.org). Just ensure your are using correct URLs of your activeCollab installation. Reports module needs the daily cron / scheduled task to be executed.