I personally don't test that way so I'll let someone else answer you re: your beeps. Thats what you should be hearing with no memory in there. I've also never heard of a Mecury motherboard before but that could just be my sheltered existance. For $35, you may have gotten just what you paid for.
The MoBo mfg link for the manual at your vendor's site is broken, so you will need to search elsewhere. Mercury is not listed as a manufacturer at WinDrivers paid site (one of my favorites for issues like this) but a Google search does produce a lot of links for a Gateway Mercury Motherboard. Oh - Oh !!!!!!
Back to your problem. Check all of your connections. Try a different stick of memory in there if you have some and re-seat both your video card and memory. As to booting with your old system's HDD, you'll need to do an XP repair install to load the correct drivers but contrary to what some others have posted, its not all that difficult to move a fully loaded system hard drive from an old computer to a new one. You will need a slipstreamed CD with whatever service patch version you had installed on the drive.