USB External Mass Storage Device Errors

Hi I hope someone can help me with my issue.

I recently purchased a Dimension 4600 w/2.6 ghz and Hyperthreading.  I hope this isn't too long, but i'm going to step through what I have done and what I think the problem is.

1.   I installed an external hardrive via the USB port, no additional drivers were  necessary.  The harddrive loaded fine and I was able to use it and safely remove it when finished.  No problems.

2.  I then installed a dvd burner (Iomega that I put in an external case) which was also usb.  When installing I got the dreaded Blue Screen.  After rebooting it appeared to finish loading the drivers and the pc recognized it.  However, when I tried to safely remove it, I would get the blue screen and have to reboot (being stubborn I tried several times).  I discovered that if I had it hooked up when initially booting it would recognize fine, and I would just shut down before removing it.  I was still having problems with it locking up during burns and I thought the problem was related. (I later discovered the burn problem was apparently a software incompatibility).

3.  At this point I decided I would just reinstall windows since I didn't have much on the pc anyway.  I did a complete reinstall and even reformatted the hd.  I also reinstalled the setup software from my dell disk.  Included the needed drivers.

4.  After the reinstall I plugged the burner into a usb port and it loaded w/no problems just has the harddrive did originally in 1 above.

5.  I plugged in the external harddrive which was originally working fine before reinstalling windows.   This time the hardrive gave me the blue screen like the problem w/ the dvd burner listed in 2 above.  And subsequently could not safely remove it.  It was like the hardrive and Dvd burner switched roles from the original installation.  It seems that the pc worked fine with the orignal mass storage device but had problems with subsequent ones.

6.  I decided that I didn't use the external hd much so I would leave well enough alone since it would work fine as long as it was hooked up prior to booting the pc and I didn't remove it without shutting down.

7.  I attempted to install my 2 printers and scanner (all usb).  My scanner installed fine, as did my laser printer.  However my HP Photosmart 7960 didn't install properly.

8.  After following the instructions from HP to reinstall my HP 7960 printer, the printer installed fine, however the Card reader portion (part of the printer) was having trouble.  In the past on other computers the install took a few seconds, but the pc showed installing the "drive" (card reader) for about 20 minutes. 

9.  At that point I decided to let it keep working, shut off the monitor and went to bed.  This morning I turned on my PC and it said the drivers were installed properly and I could see the card reader as an additional drive. I thought "great" finally everything's working.

10.  I rebooted and after seeing the windows starting message, my screen went blank and did not take me to the desktop.  I waited several minutes and finally had to manually turn of the pc.  Tried this several times.

11.  I unhooked the usb cable from the photo printer and the pc booted normally and showed in the safely remove hardware that the card reader drive was there, but of course the pc didn't recognize it because it wasn't plugged in.

12.  I plugged back in the printer and it recognized the card reader and printer fine.  Then rebooted same problem as before w/ the black screen and worked after unhooking the printer again. 

13.  This time it still showed everything as in 11 above.  I plugged the printer back into the usb port and nothing happened.  Tried rebooting and doing the same thing several times, sometimes it would recognize the card and printer, sometimes not.

14.  I then decided to try to safely remove card reader when the system wasn't recognizing it anyway, but when I clicked remove got the error, "run dll as app error"

Sorry for the book, but I think the problems are related.  It seems as though my computer is having difficulty with more than one usb mass storage device hooked up to a usb port.  I am stumped and haven't seen any similar problems posted.  Any feedback is appreciated.  Thanks in advance.