After using my samsung galaxy tab, I press the power off and ok to shutdown..for some reason when I try to use it again after some time off, there is a message on the screen which says Power Reset or unknown download mode..and it drains the battery too..the only way out is to press in power on/off on the side for about 2 minutes..is there a solution to this not happening again

SOURCE: My Galaxy Tab just hanged and the screen is off

Hello, attempt to perform a hard reset and see if the device responds at all.

1. With the device off, press and hold Volume Up and Power.
2. Release the Power button when you see the Samsung logo, but continue to hold Volume Up until the recovery screen appears.
3. Use the Volume buttons to navigate the menu and select wipe data / factory reset. Press Home to choose the selection.
4. Press Volume Up continue.
The Galaxy Tab should then go through the hard reset process.

the unit should work normally after the reset is complete.

SOURCE: My Samsung Galaxy Tab says

You're in download mode. If you're not connected to USB, then pull the battery and plug it back in. This will restart your device.

Shajan RS

• 890 Answers
• Posted on Mar 06, 2011

SOURCE: i need to download user manual for samsung galaxy

You can download the available documents from the following website.
http://www.samsung.com/uk/support/search/supportSearchModelResult.do?menu=SP01&searchWord=galaxytabpc&default_searchInputBox_value=Enter+model+number+or+keywords&searchInputBox=galaxy+tab+pc+
Please let me know if you require any further assistance.
Thanks

SOURCE: Hi, i have Galaxy Tab model

Install these drivers http://firon.net/xda/Samsung_Mobile_Driver_V1.3.800_For_SPH-d700_Epic_4G.zip for windows 32bit 
this should fix your problem

SOURCE: my galaxy tab automatic shutdown

reprogram the system