said by DonianAzar :
I use the microphone slot to record the tapes...
That's your problem right there. As mack1951
tried to explain in the second post from the top, you cannot use a mic
input with line-level
outputs, such as from a tape player. You need a stereo line
input. Some computers (maybe your old one?) have a single COMBINED mic/line input that senses the audio signal and automatically switches to the correct setting. If your new computer has only a typical simple mic input, your recordings will be distorted from over-modulation.
That's the reason I suggested the inexpensive Behringer device above. It accepts your analog line-level tape signal and converts it to a digital signal which is fed to your computer via USB, bypassing your new computer's mic input and sound card completely. To make a recording with Audacity, you have to set it up for "USB mic" recording (that's how Windows 7 somewhat incorrectly refers to any USB audio input) using the specific, detailed Audacity instructions I linked above.
If you are using the Behringer device correctly, NOTHING should be connected to your computer's mic input.