what are the specifications i need to give?
i have win 7 and xp and i only happens in win7,
sometimes when i login, when it happens it happens twice in a row,
sometimes when i connect the external hdd,
sometimes when exit bitcomet or css,
or sometimes completly ramdom...
You will at least need to give the stop error number and the numbers after it in the BSOD.
When it comes to BSODs, you should try to provide all the information you can, since just about anything can cause one. You should fill out the computer specs section in your user CP. When filling it out, you can use programs like CpuID to figure out most of the stuff you don't know.
To get crash info:
Open the start menu and type "event" click "Event Logs", Now expand the subfolder "Custom Views" and click "Administrative Events" Now find an event that stated Windows did not shutdown properly and post the details (Copy and paste, please)