I don't know much about SQL Server or MySQL. I have a web app and I had a friend help develop it so that it could be used to search my database. This database was created in SQL Server 2008 Express. It's only 3 GB. I know there are limitations on this version of SQL Server. I regret not developing for MySQL. Would I really have big issues if my web app was used by many people at once? not that I'm expecting this but I want to know if anyone has a guess on how far I can push it with the limitations of the current version of SQL
Since cracked versions can have hidden viruses I recommend then you format the server completely and reinstall the OS and SQL server. As far as getting in trouble I wouldn't worry too much when you are trying to the right thing -- they give you 30 days to register the legitimate version anyways.
Technically, you should be fine. So long as the copy you are running is valid, licensed, and obtained through a reasonable attempt at legally purchase, you should be ok.
Its the same technical premise as installing a trial copy and then registering it, so long as the latest license action is moving it to licensed status, you're good.
The question of "will I get in trouble" is a much larger legal debate related to EULAs and purchase contracts, probably better fielded by a corporate legal type.
Firstly, IANAL, but you've done the right thing by uninstalling it. If I were you, I'd relax, I can't imagine for a minute you have anything to worry about. It's your 'friend' who has done wrong, and if he continues this practise he will probably end up in trouble sooner or later.