computer hang and computer not worked while opening file

There can be several reasons when your computer not respond while opening a file. Some of that are:

Not enough memory.
File size is too big.
Your operating system not working properly.
Your CPU or RAM are old or of low configuration.

inorder to above...something more are---

- system files may be corrupted.....due to sudden shutdown of PC............
- the system may be infected with VIRUS
- many errors in the Hard Disk called as Bad Sectors