i have a wireless mouse that switches between 800DPI and 1600DPI... wich one is better and how do i know wich one i have active
can i turn this off?

1600DPI is better.

DPI means how accurate and responsive your mouse is.
The higher the DPI, the better.

Also, if you're gaming a lot, especially games that require lots of mouse precision, invest in a good mouse with a high-DPI optical/laser sensor. I have a Razer Lachesis at 5600 DPI. Best mouse I ever had, really makes a difference.

i cant invest in anything related to gaming.... not enough cash.... but... can i switch them manually from a program? the mouse came with no CD or stuff.... because i press both mouse buttons a lot and can be .... bad

Usually such mice are plug-and-play, but it might have a program that allows you to switch sensor precision from 800 to 1600 DPI and vice versa. Also, other mice (such as mine) allow you to increase/decrease DPI on-the-fly with special buttons on the mouse itself, usually right behind the mouse wheel, or on the sides. Is this the case with your mouse?
Also, check underneath the mouse for such buttons. If you can find no extra buttons, then it's probably a program - check your taskbar for applications controlling the mouse, or look online for programs that do that for your mouse model.

like RAIN27 said, it's not necessarily better to have higher DPI, as it only relates to how much you have to move your mouse around. the more DPI the faster it will move around on your screen. The mouse itself doesn't respond better due to high DPI, that would be response time.

I personally play at 3600 DPI, If I try to go higher on my mouse I don't feel like I am in control of my mouse' movement.

Try to think what is more natural/comfortable to you. Moving your mice only with your wrist or with your whole arm. Arm= low sensitivity/dpi, wrist = high sensitivity/dpi. Its all about your own preferences.

Best gaming mouse (imho) is Razer Naga ; 5600DPI , amount of buttons , you cant even use them all whatever you playe (WoW,GW,LoL,....) I have had this mouse for over a year and a half and it didnt fail in anything ever , not like other mouses , you dont need to train your muscles like a Mundo when you are trying to move your cursor somewhere . Also has its own program that can change DPI , make macros for you (press dis button and you ll have whatever you want strated ... ) I prefer higher DPI , so in your case , I d advice you to switch it to 1600 DPI (still makes difference ) .