I really don't understand much of the stats and accounts or anything.

What I know is that I want to donate computer power, and I have done so for a number of years. But I don't have time to investigate into the different quirks of BOINC, and CPID and RAC and World Cup or anything. I only want to donate cpu time. That's enough for me.
The problem is that I have signed up to different projects with different emails.
And now I have a hard time finding my total stats.

I have signed up with at least 3 different emails.
I am able to find (some of) my stats when searching for my username. But I cannot remember whether I used the same name with all projects: Cronos. So there I am. How can I find my total stats? Why cannot the BOINC client itself aggregate the stats and send the totals?
And now I had to sign up with yet another account (to join this site). It's all so confusing.

I think my username is Cronos. But I see that MilkyWay@Home has me as "Temahot", and I'm not sure if I've used the same username consistently. But I DO know the various emails/passwords to the various accounts..
I've tried attaching some projects to this BAM account, but... I see that several projects are still missing.

So what to do?
Which is which?
And why can't there be one central account?

Any help would be greatly appreciated.

Cleanup the mess is my first reaction

The good thing is that you wrote:

What you have to do to gather the stats in 1 account is use the same e-mail address and password for all the projects
AND for your account here at BOINCstats if you want to use BAM!.

After synchronizing the addresses you should wait 1 or more days to give the projects time to all get the same CPID.

BOINC is just a software package; there are no services provided by it or its developers relating to stats or the work being done. All of the projects are independent, and have their own servers for managing the work sent out, forums, website, stats, etc. The concept of an account manager (which BAM is) was developed to help tie everything together in a way that is easier to manage, but the account managers are also independent from both the BOINC team and the projects. Even though BAM does a lot of things for you relating to project and client management, there isn't any real link between BAM and any of the projects. It just does these management tasks on your behalf, and to keep things simple the current way of doing this is to use the same email & password for all the projects that BAM manages.

The good news is that email, password and account name are all things that can be changed, though only at each project's site. Once you have everything under the same info, it might take a few days for the stats and everything else to line up. The best way to prevent headaches in the future, is to only use BAM to make changes to the projects you participate in. That way, you know the same information will be used on all projects.

Thanks for the answer. I changed the emails to each account, and now I am partly updated. There are still some strange things going on, though...
I still miss stats from LHC, Simap, and Tanpaku. These don't show in "Overview" mode (when I search for my username), and also not in "Detailed" mode.
There is also another user which I think is me -> Cronos in Norway.
Also, when I click "host", nothing shows up, whereas prior to the update, I had the correct cpu etc.

And when I log in to Simap I can see under "Projects in which you are participating" only SIMAP and Tanpaku, but on the LHC account, I am listed with ClimatePrediction, Rosetta, Einstein, Ibercivis and Milkyway (but NOT SIMAP and Tanpaku).
They have the same email and password....


And how do I do this?

I have now managed to claim most of my credit, and merge everything into one "user" but now my history is gone!
I have only 3-4 days of history now...

Isn't this idiotic! I hope you understand my frustration.

Yes, when you changed your email addresses to be all the same, the Cross Project IDentifiers changed. The stats sites, including this one, rely on the CPIDs in order to track things.