if you meant that you want to cut power to the device and force it to reboot, just remove the battery.

(i've tried many different apps and things on my n800 and never experienced a speed decrease unless i was trying to do too many things at once or move a very large amount of data via USB. even then, i could usually kill the offending app using loadapplet. anyway, i'm guessing that rebooting should get you your speed back.)

p.s. my spanish is much worse than your english, i can assure you....