I am running Windows 8.1 on my Sony Vaio laptop and want to run a Linux-based OS from a bootable USB. Can anyone tell me whether my Windows will be safe during and after the booting process or I'll lose all the data, softwares, files, etc. ?
If you are booting live from a USB or CD you can read/write to the windows partition. Therefore you can screw something up, if you are messing with system files on the windows partition.
You can safely play in the Linux OS environment just don't touch Windows System files or play with the partitions (unless you know what you are doing), and you will be fine.