steam acting up

To "reinstall" Steam, you simply delete everything in your Steam folder except the steamapps folder (so you avoid to re-dowanload every game) and steam.exe (if you run it afterwards, it will download all the missing stuff).

Btw: That's the default answer you get from Steam support if you contact with any problem, even if your problem is not the least related to a faulty installation or startup problems. (your experience may differ)