1. Are you able to control other functions on the PC with the remote? If not, check that you've the correct drivers installed, such as for the IR connection.
2. If you're wanting to "turn on" the computer with the remote, to the best of my knowledge, that is not possible. I did recently reinstall a home media PC with Win7, and was able to bring the computer out of sleep mode... but not from totally being turned off. I also don't think it's readily possible once the computer has gone into hibernation. I believe the reason for all of this is that the remotes only work within Windows, and not at the BIOS level.
I'd be more than happy to find out I am wrong on this, b/c that would mean that it's just something to learn rather than being stuck without the possibility.
One idea is that you could look at the "power on" events in your BIOS settings to see if any options there might work.