[Q] Help! I can't go use flashtool after using cm10 [tipo] topic

So I use an st21i, and I got curious with cm10 because I didn't like the ics that much. But ever since I used cm10 [it's still what I'm using], I would turn on the debugging so I can use flashtool but it will only recognize it when the phone's turned on. Which means I can't go to flash mode or fastboot mode [though the light indicator says it's on that mode] flashtool itself tells me that I should put it on flash mode/ fastboot mode. And the moment the phone turns off for any of those mods my laptop would say that USB device unrecognized and all that stuff. I want to go back to stock ICS but I can't use flashtool, and I don't know where I can get the stock kernel. Please help me! Thank you!