i've problem with my computer for long time, i don't know what it is, clearly i can't use my computer as mine. i can't  instal or uninstal a program because environment different. and windows can't find %windir%/system32/rundll.exe. and troubleshooting say to ask administrator. what should i do? thanks

Boot up in Safe mode, open Command Prompt and type in the following command followed by hitting the Enter Key:

 sfc /scannow

Hello arbolpurba,

Please go to C:\Windows\System32, and check if you can find the file rundll.exe.

Please try to copy or replace the rundll.exe from the other normal Windows 7 computer.

Additionally, please use the system restore to help you restore your computer's system files to an earlier point in time.
http://windows.microsoft.com/en-hk/windows/what-is-system-restore#1TC=windows-7

Best regards,
Fangzhou CHEN