yes it is normal, and it may be affected by the storage format, or the hardware itself.
does the hiss occur when there is no music playing? or only when the file is playing?
is the file converted from an analog recording to digital? There could be hiss on the original recording that was converted to digital format.
does the hiss occur when a CD is playing, or with other music file types not mentioned like MP3?Look in "My Music" folder, for sample music and try the playback, still hissing? are you using media player or some other player?
turn the volume of the player up, at ;least 50% or higher. Turn the master volume of the computer down.
The speaker icon is in the lower right hand of the desktop, click once for volume control (computer master volume) click twice for mixer, or other audio software. You might need to raise the player and lower the master volume, to find a better signal to noise ratio.