Don't bother with ATK ( advanced task killer ) see link
http://www.kandroid.org/android_pdk/power_management.html
oh and some info i lifted from another site
I'll add a bit more info on memory managment.
By default Android will keep the last used applications loaded into it's memory. It requires less power to keep them in the memory than it does to kill them and load them later on. (booting an app requires the CPU, which happens to drain the battery VERY quickly)
When for some reason it needs to load a new app and free memory for that, it'll kill selectively. The ones that are most likely to be used again are kept in the memory, and those that aren't needed are killed.
How does Android determine which ones to kill and which ones to keep? Easy.
The phone logs just about everything. Which apps you use, how often you use them, which apps are used by the system, when certain apps will poll for new data (like the mail app polling it's server), etc.
It then uses all that information to determine the memory and power managment, so that it needs to use the CPU less and has the necessary apps already loaded into the memory when you use the phone.
It takes a few days for the OS to log sufficient information and adjust itself accordingly, which explains why the first few days after a factory reset or a major OS update are always tough.
All this can only happen properly if Android gets accurate data. Using a taskkiller will only confuse the OS and will kill apps that would have been better off if left alone. Yes, you'll save some energy by not having all these tasks loaded, but the extra CPU usage to boot them again easily outweighs that.
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On a more personal note :
The first app I installed on my Desire (my first smartphone) was Advanced Task Killer (otherwise known as ATK). I did that because many people told me that it was absolutely necessary if I wanted to have any battery life at all.
After 2 weeks I had around 50 hours of battery life and was happy about that.
I then read a post about taskkillers and decided to remove it as a test (although I was very skeptical).
The first 2 days I had no battery life to speak of, but afterwards I noticed an improvement in speed (because the right apps were always loaded) and saw my battery life increase to 55-60 hours.
Music blaster is a get app for downloading mp3's
