Twice I recorded songs from albums and the result have been the same. The music sounds like it was recording in a tin can.
I have Win 7 and I have to go into the Mixer and disable the "stereo mix" sound source otherwise I hear a pronounced reverberation, like a tin can. Your set up is likely different, try muting the sources in your mixer until the sound is clean.
Not sure of how your record player is hooked up to your receiver but here is something to consider.
Phonograph records need to have their signals equalized via an industry standard RIAA Equalization Curve.
see this link to explain it in detail: http://www.graniteaudio.com/phono/page5.html
Unless you hook the phono cartridge to the Phonograph input on your receiver you will get a very thin sound like you describe. Many new low end receivers no longer have a Phonograph input, so you may have to buy a Phono pre-amp to not only get the sound adjusted properly, but also to bump the power up to "line level".
Check here if you're not familiar with that term. http://en.wikipedia.org/wiki/Line_level
One other problem is that you may be feeding a line level signal into a microphone input which is expecting only a fraction of the power you are feeding into it. You may be massively overdriving your input. Some systems will automatically compensate for this overload and you may be alright there. Since you haven't blown out the input yet tells me there might be some adjustment going on.
I have audiophile equipment that has the built-in phono pre-amp, but you can fine separates all over the internet with prices into several hundred dollars. I have no experience with this particular device, but this is the sort of thing I'm referring to: http://www.amazon.com/TC-750-BLACK-Audiophile-Phono-Preamplifier/dp/B000A36LQ4
Hope this helps narrow down your problem. Good luck