Cannot upgrade firefox

Computer Type: PC/Desktop
System Manufacturer/Model Number: eMachines ET1810-03 (Acer) - single user
OS: Windows 7 Home Premium - always up to date
CPU: Intel E2210 2.2Ghz
Motherboard: (OEM) ECS MCP73VT-PM with AMI BIOS R01-A3 (4-29-2009)
Memory: 3Gb DDR2
Graphics Card: NVIDIA GeForce 7050/610I GPU
Sound Card: Realtek ALC888/1200 8-channel HD integrated
Monitor(s) Displays: AOC 22" LED
Screen Resolution: 1920 x 1080
Keyboard: Wireless
Mouse: Logitech M705 laser wireless
Hard Drives: Internal - Seagate 320Gb SATA; External - Western Digital 320Gb USB (3.5" internal drive inside a RocketFish USB enclosure)
Internet Speed: TWC Cable Broadband ~ 15 Mbps Down/1 Mbps Up
Browser: Chrome
Antivirus: NIS
Other Info: Microsoft Office 2007, incl Outlook SP3; Netgear router; ubee modem

System Manufacturer/Model Number: Hewlett packard/p6512uk
OS: Microsoft Windows 7 Home Premium 64-bit 7600
CPU: IIx4 amd athelon 635 processor
Motherboard: FOXCONN 2AA9
Memory: 2x2gb
Graphics Card: ati radeon HD 5450
Sound Card: (1) Realtek High Definition Audio (2) AMD High Definition
Monitor(s) Displays: samsung lcd tv 32"
Screen Resolution: 1360x 768
Keyboard: wireless hp
Mouse: wireless Hp,optical
PSU: ?
Cooling: air!
Hard Drives: (1) WDC WD10 01FAES-60Z2A0 SATA Disk Device (2) Maxtor OneTouch USB Device (3) ST310003 33AS USB Device (4) WD My Book 1111 USB Device
Internet Speed: 1.10mb/s
Browser: Firefox
Antivirus: MSE