my imac is giving me an error message

hi if anyone can please help id appreciate it
when i turn on my imac i get the apple logo
with a progression bar that progresses about less than half way
the screen then turns white for a minute, reboots and does the same thing over and over

when i ran an apple hardware test on the imac i got the following error message
can someone please interpret it for me and tell me what this means...

The error message is 4m0t/4/40000003: HDD -1328

Thanks in advance..
it is noteworthy to mention i had installed an adobe flash player update very shortly prior to this occuring.
Can someone please help?

Again

Thanks