Hey Guys,
I'm stan450, and me and my friend have lots of cool ideas for 2d games (which are veerryyy possible), and we have just started on the learning part. Any advices, guys?

Start with simple games (pong is awesome to start with), then move on to slightly more complex games (pacman, breakout, tetris, etc) , Look at the games from the 70s for inspiration, there are tons of great ones that are fairly easy to make and when you feel ready try to tackle a project of your own design (Designing games that are easy to implement is a good way to grow as a designer aswell)

Edit:
Seem like my grogginess this morning made me completely not see the actual topic xD Still, I'll keep the reply:

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Here's my advice:

Don't limit your ideas, but instead group them up into two groups - (1) very compact "must-have" features that you need to be absolutely certain that are doable (this is the core vision). Support these by (2) a large, highly imaginative list of "should-haves" (what you want in the game - the "wall of crazy"). That way, you'll always have something good to fall back on, and the "should-haves" are just additional aspects of that, either added or not. IMO, every chapter of the design document should have a wall of crazy ideas (provided you can come up with them), or a "wall of crazy" addendum where all the ideas are piled up.

Then, follow the "must-have" design document like a brainless sheep (no joke, but nothing personal either). Do not sway from it, even by an inch (unless it's the lead designer making a necessary change (e.g. after playtesting) that is clearly pointed out to ALL parties). The addendum "should-have"s, on the other hand, is something you can add or remove stuff to on the fly.

I'm thinking that the addendum ideas should have two states, either "wanted" or "implemented", the latter obviously following the same rules as the "must-have"s.

Also, what would be ideal computer specs for programming C# with XNA ( Like processor and stuff)?
EDIT: By computer specs, I mean what would be an ideal computer to start out on.
My current specs are:
GA-69GM-S2H
MSi Radeon HD 5450
AMD Athlon X2 Black 6400+
2GB DDR2

That's more than adequate for developing in C# and XNA, especially if you're working in 2D. If your game lags with those specs, you can rest assured you've designed it in a way that is resource-inefficient.