Problems uploading sketches to UNO R3 using Arduino IDE

Hi. I recently got an Arduino board; an UNO R3 from Inland Electronics with an ATmega328. I know that has a bootloader because it has Blink pre-uploaded; whenever I plug it in to my computer, the pin 13 LED flashes every other second. Since I have had it, I have not been able to upload any sketches to the board.

I am using the Arduino IDE 1.6.7 on a computer running Windows 10 64-bit. I have researched my problem and have been unable to find a fix, albeit trying everything that I can find. I have been trying to upload a slight modification to Blink, to make the LED blink faster. Nothing is connected to the board other than the USB cable to the computer.

I will begin by sharing the main error message I have received, then give some additional information. My error message:

Arduino: 1.6.7 (Windows 10), Board: "Arduino/Genuino Uno"

Sketch uses 1,030 bytes (3%) of program storage space. Maximum is 32,256 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2,039 bytes for local variables. Maximum is 2,048 bytes.
C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avrdude -CC:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf -v -patmega328p -carduino -PCOM3 -b115200 -D -Uflash:w:C:\Users\(my username)\AppData\Local\Temp\build9c9ef3bdfe2fccb480bc6e4bac749e41.tmp/Blink.ino.hex:i 

avrdude: Version 6.0.1, compiled on Apr 15 2015 at 19:59:58
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2009 Joerg Wunsch

         System wide configuration file is "C:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf"

         Using Port                    : COM3
         Using Programmer              : arduino
         Overriding Baud Rate          : 115200
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xcf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0xcf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0xcf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0xcf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0xcf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0xcf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0xcf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0xcf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0xcf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0xcf

avrdude done.  Thank you.

Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

  This report would have more information with
  "Show verbose output during compilation"
  enabled in File > Preferences.

I have tried pressing the reset button at various different times in the process, for varying lengths of time, to no effect whatsoever. Some more information follows:

-All USB connections are secure
-The RX LED flashes briefly after each "attempt"
-All drivers are up to date and installed
-In Device Manager, my Arduino is shown as "Arduino Uno (COM3)". No other COM ports are shown as being used
-I have selected "Arduino/Genuino Uno" under "Board" in the IDE
-I have selected "COM3 (Arduino/Genuino UNO)" under "Port" in the IDE
-The programmer that was selected on installation of the IDE (and that still is selected) is "AVRISP mkll"
-I have changed the COM port to COM4 resulting in:

avrdude: ser_open(): can't open device "\\.\COM4": The system cannot find the file specified.

-I changed it back to COM3 resulting in:

avrdude: ser_open(): can't open device "\\.\COM3": Access is denied.

-I then completely uninstalled the Arduino software (after disconnecting the board)
-I followed the steps to reinstall on the "Getting Started With Arduino" page on this site
-I then began getting the original error again

I shared this information based on what other threads have mentioned as being fixes (none of them worked for me). I also have another few interesting things I found in Device Manager. In the Properties dialog for my Arduino, under the "Events" tab, three things caught my eye. They all have the timestamp of the second I performed driver installation.

The first:
-Title: Device not migrated
-Description: Device USB\VID_2341&PID_0043\75439323735351700240 could not be migrated.
Last Device Instance Id: USB\VID_05DC&PID_A81D\AA9KP05KDCSEH9PK
Class Guid: {36FC9E60-C465-11CF-8056-444553540000}
Location Path: PCIROOT(0)#PCI(1400)#USBROOT(0)#USB(2)
Migration Rank: 0xF000FFFFFFFF0023
Present: false
Status: 0xC0000719

The second:
-Title: Driver service added (usbser)
-Description: Driver Management has concluded the process to add Service usbser for Device Instance ID USB\VID_2341&PID_0043\75439323735351700240 with the following status: 0.

The third:
-Title: Device installed (arduino.inf)
-Description: Driver Management concluded the process to install driver arduino.inf_amd64_298a9936aef7c163\arduino.inf for Device Instance ID USB\VID_2341&PID_0043\75439323735351700240 with the following status: 0x0.

Not sure if any of those three things have any significance, but wanted to share anything that might help.

I really hope I can get my new board working soon, and I would greatly appreciate any help that you could provide. Thanks in advance!