I can't get him to stay at Lakeview Manor,is this because I already have a horse there?

Possibly. I'm not sure, but if you buy a horse for your new house then it counts as an owned horse and will replace any other.

If you have the Summon Arvak do that and I don't know if you have to ride him or not but I did and Shadowmere stays at Lakeview for me. I've done it twice because when bandits attacked both horses opened a can of whoop a** on them and when I moved Shadow back to the house he followed me on my next fast travel. Stretched Arvaks legs a bit at Lakeview and Shadow stayed.

And I have horses at all three houses and Shadow is not replaced.

You have to ride Arvak if you want to make him your current horse. My only problem with Shadowmere is getting him to stay near the house. He keeps rushing off to fight things and will not automatically return to where you left him. So Braggen has to ride him back to the stable each time, then summon Arvak again, and ride him for a few seconds. After so many problems with attacks on Lakeview Manor Braggen has not bothered buying any stock this time, so Shadowmere has the stable all to himself, but still usually prefers to stand outside.

Yeah, I also prefer not to buy a 2nd horse. I just keep Shadowmere inside the stable.

I didn't even know you can make your horse stay in the stable and not follow you on fast travle! how is this achived?

The easiest way is with the conjuration spell Summon Arvak, summon Arvak and your old horse will stay put wherever it is standing. However, Shadowmere can be killed and will respawn where it died 20-30 days later, and will not follow you/appear after it respawns.

thanks Frank thats very good to know:) gotta love these forums!

I have a horse and a hose with carriage and Shadowmere still appears.

I had some simular problems with Frost now I can't even find him / her have no idea where I lost them Last I saw they were floating down river fighting...

~NS