Try starting with your line-in level very low, BlueJay. Overload levels sound terrible in digital audio. If it doesn't sound good at low levels, take the mike back to Walmart. (Overload levels can sound great on tube amps but your autoharping may sound more like a Jimmy Hendricks recording.)

If low levels sound good, bring the levels back up a bit at a time until you find the limit. Also, if it sounds good, try taping the mike to the instrument with masking tape and recording at low levels. (Fold both ends of the tape under for easy removal.) Again, bring the level up until just before it hurts for best sound quality. Fastening the mike to the body of the instrument works well with cheap condenser mikes that use batteries. Cheap condenser mikes often outperform more expensive dynamic mikes costing $200 - $500 Canadian. I've seen clipon condenser mikes advertised for as little as $1.50 on the internet. Clipon mikes are not directional so they pick up room noise.

If you can't find a cheap condenser mike, you can buy the condenser cartridges and build you own mike. Condenser cartridges cost (approximately $5 Canadian = $3.50 U.S.) at Radio Shack or ($1.50 Canadian = $1.00 U.S.) at Electrosonic and Active Surplus in Toronto. The mikes are made from one condenser cartridge, one resistor, one capacitor and one battery. The larger cartridges sound better. You can make your mikes directional with toilet paper rolls or cans and cotton swabs. Cover everything with cotton except a recessed opening at the front of the cartridge.

I have never made a condenser mike myself. I bought cartridges for experiments but haven't yet found time to spend with them. I have mounted cheap condenser mikes with cotton puffs in old dead mikes and mounted them on instruments. The results were pleasing. Also, I bought four discontinued, decent quality, directional, condenser mikes from Radio Shack a few years ago for $70 Canadian each (about $50 U.S.). They seem to be identical to Shure studio condenser mikes that were selling for over $300 back then. In tests, the Radio Shack condenser mikes sounded noticably better then a $500 German mike and much better than Shure SM58s, the most commonly used stage mike. Yet, $22 condenser mikes with large cartridges (no longer carried by Electrosonic) sound even better than the Radio Shack mikes and cotton is cheap. Check out you local electronics stores and anyone selling cheap used equipment. Experiment. Have fun. Playing with mikes is very safe from an electronics standpoint. You can't do much damage.

You'll need to record at least 16 bit, mono, 22k, for decent sound quality. Chews up the hard drive at about 1.25 meg per minute though, I believe - 16 bit, 44k, stereo, gobbles about 5 megs per minute record time.