Bonus clearing at party skins

[jakbse]

Late July I was tired of waiting for a reload bonus offering from Party, which until that point was the only site I had played. I started looking for alternatives and found Multipoker which had a decent sign-up offer and works fine with PT.
I signed up, made a maximum deposit of $500 and started to play.
Later I have heard that you need to use a different computer when you sign up for a party skin. I don’t know why, I used my ordinary computer without any problems.
Which are the rules that apply? I don’t want to cheat or put myself in any sort of trouble. If I had heard this before I went to Multipoker I would have signed up for Abolute or whatever instead.

[nervous]

You were able to have party poker AND signup for multipoker on the same computer without modification? Don't worry about having accounts at each of their sites, it's just they generally don't allow signups from the same computers.

Nothing to worry about and have fun clearing the bonus.

[jakbse]

Well, I might have done the sign-up procedure from another computer. I have three of them at home standing next to each other. Their all behind the same router so it's definetly the same IP.
What's the reason not to allow signups from the same computer and how do they track the computer if it's not by IP number, cookies?