Hi this is another acount that i created today, because i have another acount at lvl 30 but aparently i can't log in with it (my last time online was on 2011) i tried all passwords and even try to send my login id to my mail... but the page says that my mail isn't linked with an acount.
After that i created this acount and try to put my mail, but it says that my mail is in use. I don't know what to do and if you can help me it will be great.
Thanks for your time =D

It sounds like your account was compromised, and the password/email/summoner name could have all been changed. Send a support ticket to support and check out some of this information to keep your account safe:

I suggest checking out Riot's Account Protection page in Support (HERE)

I also recommend getting a secure web-browser. Firefox & Google Chrome are my two recommended web browsers. If you've already got either/or installed, install the addons NoScript (Firefox)/ScriptNo (Chrome) and then AdBlock Plus (For both browsers) to ensure you account cannot be hijacked so easily.

Make sure not to click links in emails and keep in mind that Riot will never ask you for your passwords.