What flash does what?

Hello everyone, I am a newbie here with newbie questions. I am new to this flash cart thing as well and know just about nothing. I hope I can learn everything there is to know about it, the easiest way possible, and be able to play some of the older games. Are the games only limited to only Nintendo or is there a way to play games like Sonic?OK, my systems on hand are a few DSL's, DSi's and one 3DS.DSL's are all up and running perfect. I just aquired 2 DSi's that have an error message anytime I touch an application on the screen, says something error has occured and needs shutdown. I can operate the camera by using the bumpers, so they take pics and store them but I can't access them once saved. I have been reading and it seems that using a flash card may fix them. Any help with this would be great and I thank you in advance.What card would work best for my needs? Can the card be used between any of my systems, without any modifications to it, between the switches?Post Merge: [time]1338682755[/time]
After reading a bit more on this site it looks like acekard is something that will fit my needs, but will it fix the error messages on the dsi's?I also read a little about the Supercard DSTWO and wonder if the added expense is worth it. Are there many more games available to the Supercard to make it worthwhile?

Thanks for some starting points. I have never used any of these cards as I don't own one. The 3DS was purchased new so it is updated but it's working fine. I purchased the DSi's used and don't know their history. I really am just hoping to get the dsi's working and if I can get a few extras while doing it would also be great.I would just like to go for one of the less expensive ones to see if I can make it work and maybe later on if I get used to it I'll get the more involved expensive oneI guess right now it comes down to who has the best service and price on either that r4 or acekard..Post Merge: [time]1338730368[/time]
After some reading on this site it seems to be a toss up between R4i Gold and AceKard2i. I just came across this one: http://www.dsflashcart.com/r4i-sdhc-3ds-flashcart-for-your-ds-dsi-3ds-p-250.html and wanted to know what is the difference between it and the Gold other than a few bucks less, should I stick with the Gold/AceKard2i