Hi i have a canon 450d dslr camera. when i take a picture and take a look on the LCD screen only the top half has come out while the bottom half is black as if something is obstructing the lens plus its struggling to focus. The battery was low could that be the reason?

Your camera is working exactly as SLRs have worked for the first half-century since their invention. You frame the picture through the viewfinder then take the shot. The display is for menu settings and reviewing pictures after they've been taken. Newer DSLRs will let you use the display for picture-taking (and take videos) but the A200 belongs to the previous generation.

cables on the LCD screen needs replacement go to the nearest service center

In menu option C.Fn-12 you can choose to switch the display off (or on) when you switch on the camera. The display stays off even if you switch of and on the camera.
Press the button <DISP> and switch off the camera, while the settings for recording are on the screen. After you switch on the camera, the LCD screen will be switched on again.
Please refer toy your english manual, I had to translate, because I don't have the English version.

i bought one lens oh this and till now i could not focus ny shoot :( in manual can you help me ... i've got a sony dslr a300

Error 01 means that communication between camera and lens is faulty. Try to clean lens contacts.

In picture taking mode, press the "set" button for "live view".

It's probably dust on the sensor. You can clean it yourself but you will need to educate yourself on the procedure and get the proper equipment. Google the words...how to clean a dslr sensor.

Check if the card is truly write protected (check the little slider on the SD card). Its possible it slid into lock position accidentally

Use a card reader to download your pictures to a folder you create on your desktop.

cant be done you need the new 450d which has live view so you view the lcd when taking the picture