What is pagefile.sys

Pagefile.sys is a windows system files, acts as swap file and was designed to improve performance. Windows uses it as RAM in case the application you're running on your computer ends up needing more RAM than you actually have. Usually page file is 1.5 times than your actual physical memory size, it is the recommended minimum size. The maximum size is 3 times than your actual physical memory size. Pagefile.sys is a hidden file. It means that you could see it in windows file manager only if you checked 'Show hidden files and folders' in Folder Options. 

As a system file you can’t simply delete it as you would for, say, a file that you yourself created but no longer wanted on your computer. To do so set both initial size and maximum size to zero, or click No paging file (Just right click on the workplace icon - either in start menu or on desktop - and select properties -> advanced -> performance options) then restart your computer. Your computer is no longer using pagefile.sys, and you can delete it now. To recover the pagefile.sys set some values to both initial size and maximum size the same way mentioned above. Microsoft strongly recommends that you do not disable or delete the paging file.

Note: Any malware can be named anything - so you should check where the files of the running processes are located on your disk. If a "non-Microsoft" .exe file is located in the C:Windows or C:WindowsSystem32 folder, then there is a high risk for a virus, spyware, trojan or worm infection!