how can i buck up my data which are located in a computer with a corrupt window, i cant access my computer and i want to format it to install new window but data in it are most important, i must not loose them
If you have another computer available that works, I would use an external hard drive enclosure for this to backup your files to the working computer. An enclosure can be picked up fairly inexpensively. Make sure you get one that matches the size (2.5" or 3.5") and interface (SATA vs IDE/PATA) of your current hard drive. Basically you remove your hard drive with the corrupt Windows on it, pop it into the enclosure, hook it up to your working computer and copy over whatever you need to save.
Depending on the amount of data you need to recover, you can instead use an Ubuntu Live CD/USB to boot into that and then copy your files to a USB flash drive or external hard drive.
remove the hard drive from that computer, plut it into another computer. The easiest way is to have a USB to IDE adapter so you dont have to open the target computer. The hard drive will be available from another system where you can just copy the data that you want to save.
Or you can always resinstall Windows over this corrupt OS. AS long as you do not format the drive, your data will still be there. My suggestion is for you to get the data off of the drive before you try to install a new OS, just to make sure you do not overwrite any data.