My Computer Freezing, Closing Explorer, USB Devices Not Recognized

So I have an iPod and external hard drive connected by USB.My Dell only recognizes these devices maybe 50% of the time or so, unless I start with the iPod connected, which will work fine. If I start with the external hard drive connected, it isn't recognized until I reconnect it. I had USB recognition problems, and Dell sent me a new motherboard for my Inspiron E1705, which I installed myself successfully. Now my computer recognizes my printer consistently, but the hard drive and iPod are iffy.I disregarded this and tried to add more music to my iPod. At first, it was giving me disc writing errors. Later on, it would either freeze or only add a small portion of the songs. So I started fiddling around with the order things were connected, and now My Computer freezes when I open it. I restarted my laptop, tried a diagnostic in iTunes (with the iPod attached at startup, which opened iTunes, then closed iTunes so I could turn on my external hard drive where my music is stored, reopened iTunes where music worked by iPod wasn't being recognized by iTunes), and it said I was having iPod connection problems.