Windows 7 - help needed for windows 7

my windows is nt openning some error is happening. it comes till welcome.pls help

Would you be more specific about what happened?
How it went? What happened before the problem?
Did you do something to it? such as installing new program, adding new hardware, shutting it down improperly, or, else?
By providing more details here, we will be able to see any possible way to help.

satyrday i copied some data and saved it in to a file .the data was form a very trusted site.then when sunday i switched on the computer microsoft logo came till welcome everything was ok.then it says tht windows is not able to open due to some errors .

It looks like you haven't done anything wrong with it.

But first, let us look into what you said as "copying data". When you said from trusted site then it could be meant as you were downloading it, right.? (give little more details).
If so, do you have any antivirus, firewall, additional security feature installed?

There are a lot of bad websites have their way try messing up with anyone by only single look harmless click. Any virus, adware, or malware might have its way into your system in that case.