Nothing happens after clicking START button

[TosunA]

ntdll.dll errors are a sign of a core OS issue with either hardware, software, or drivers. I also run Windows 7 Pro SP1 and I do not experience the same errors you do, despite also being fully updated; but there might be an update specific to your system that has corrupted ntdll.dll. Disable any overclocks you may have and run some RAM tests and HDD SMART tests.

I think you won with that part of your sentence: "but there might be an update specific to your system that has corrupted ntdll.dll"

I installed AVAST and Spybot S&D and they found a lovely one: Win32:Jeefo. Infected 423 of my files (portable executable - PE). Trying to get rid of it, but I think that will be the problem. Will make a reply, if it was successful. Anyway I can't understand where I got that worm, because my windows is freshly installed (on last Friday) and I didn't even surfed on the internet, except chatting on facebook and on TS.

Problem solved, the Win32::Jeefo was the source of it. Got rid of it after some hour, but now everything runs smoothly Thanks!