How do I know if I lost my PC's data? (HELP!)

My home PC gave it up.

It's an HP Pavillion dv9500 (and was) running Windows Vista Home Premium.

On Sunday evening I was using it. I think I left it on stand-by when I went to sleep.

My mother in law came to our house on Monday during the day. While I was at work, she called to ask: "Hey, why doesn't your PC start when I push the on/off button?"

It was dead.

The power cord seems okay since it has this little blue light at the computer-end.

I took the battery out for a while, then put it back in to see if it would make any difference. Nope.

When I plug in the power cord and put my ear against the bottom of the PC, I can hear some "electrical" sound coming from hard disk 1.

My hope is, of course, that the data aren't lost. But how can I be sure and get them out?

HELP!

I'm really nervous about this because I didn't make sufficiently timely backups.

Yes, Robert Scoble, you told us so. I got bitten.

(Did I mention: HELP! ?)