Here is the info from Trouble Shooting Firefox:

Application Basics
------------------
Name: Firefox
Version: 26.0
User Agent: Mozilla/5.0 (Windows NT 5.1; rv:26.0) Gecko/20100101 Firefox/26.0
Extensions
----------
Name: Adblock Plus
Version: 2.4
Enabled: true
ID: {d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}
Name: Ant Video Downloader
Version: 2.4.7.16
Enabled: true
ID: [email protected]
Name: Antmark extensions
Version: 0.7.3
Enabled: true
ID: [email protected]
Name: Facebook Share Button
Version: 2.0
Enabled: true
ID: {d4e0dc9c-c356-438e-afbe-dca439f4399d}
Name: HP Smart Print
Version: 2.1.0.235
Enabled: true
ID: [email protected]
Name: Lightshot (screenshot tool)
Version: 3.1.0
Enabled: true
ID: {394DCBA4-1F92-4f8e-8EC9-8D2CB90CB69B}
Name: Troubleshooter
Version: 1.1a
Enabled: true
ID: [email protected]
Name: Microsoft .NET Framework Assistant
Version: 0.0.0
Enabled: false
ID: {20a82645-c095-46ed-80e3-08825760534b}
Important Modified Preferences
------------------------------
accessibility.typeaheadfind: true
accessibility.typeaheadfind.casesensitive: 1
accessibility.typeaheadfind.flashBar: 0
browser.cache.disk.capacity: 358400
browser.cache.disk.smart_size.first_run: false
browser.cache.disk.smart_size.use_old_max: false
browser.cache.disk.smart_size_cached_value: 358400
browser.places.smartBookmarksVersion: 4
browser.search.useDBForOrder: true
browser.sessionstore.upgradeBackup.latestBuildID: 20131205075310
browser.startup.homepage_override.buildID: 20131205075310
browser.startup.homepage_override.mstone: 26.0
browser.tabs.loadInBackground: false
browser.zoom.full: false
dom.mozApps.used: true
extensions.lastAppVersion: 26.0
font.size.variable.x-western: 24
gfx.blacklist.direct2d: 3
gfx.blacklist.layers.direct3d10: 3
gfx.blacklist.layers.direct3d10-1: 3
gfx.blacklist.layers.direct3d9: 3
gfx.blacklist.layers.opengl: 3
gfx.blacklist.stagefright: 3
gfx.blacklist.suggested-driver-version: 6.1400.1000.5218
gfx.blacklist.webgl.angle: 3
gfx.blacklist.webgl.msaa: 3
gfx.blacklist.webgl.opengl: 3
network.cookie.cookieBehavior: 1
network.cookie.lifetimePolicy: 2
network.cookie.prefsMigrated: true
places.database.lastMaintenance: 1389313387
places.history.expiration.transient_current_max_pages: 26570
plugin.disable_full_page_plugin_for_types: application/pdf
plugin.importedState: true
plugin.state.np32dsw: 2
plugin.state.npdeployjava: 0
plugin.state.nppdf: 1
plugin.state.nprndlchromebrowserrecordext: 0
plugin.state.nprndlpepperflashvideoshim: 2
privacy.clearOnShutdown.offlineApps: true
privacy.cpd.offlineApps: true
privacy.cpd.siteSettings: true
privacy.donottrackheader.enabled: true
privacy.sanitize.migrateFx3Prefs: true
privacy.sanitize.sanitizeOnShutdown: true
privacy.sanitize.timeSpan: 0
security.default_personal_cert: Select Automatically
security.disable_button.openCertManager: false
storage.vacuum.last.index: 1
storage.vacuum.last.places.sqlite: 1388592965
Graphics
--------
Adapter Description: Intel(R) 82945G Express Chipset Family
Adapter Drivers: ialmrnt5
Adapter RAM: Unknown
Device ID: 0x2772
Direct2D Enabled: Blocked for your graphics driver version. Try updating your graphics driver to version 6.1400.1000.5218 or newer.
DirectWrite Enabled: false (0.0.0.0)
Driver Date: 4-25-2005
Driver Version: 6.14.10.4308
GPU #2 Active: false
GPU Accelerated Windows: 0/1 Basic Blocked for your graphics driver version. Try updating your graphics driver to version 6.1400.1000.5218 or newer.
Vendor ID: 0x8086
WebGL Renderer: Blocked for your graphics driver version. Try updating your graphics driver to version 6.1400.1000.5218 or newer.
windowLayerManagerRemote: false
AzureCanvasBackend: skia
AzureContentBackend: none
AzureFallbackCanvasBackend: cairo
AzureSkiaAccelerated: 0
JavaScript
----------
Incremental GC: true
Accessibility
-------------
Activated: false
Prevent Accessibility: 0
Library Versions
----------------
NSPR
Expected minimum version: 4.10.2
Version in use: 4.10.2
NSS
Expected minimum version: 3.15.3.1 Basic ECC
Version in use: 3.15.3.1 Basic ECC
NSSSMIME
Expected minimum version: 3.15.3.1 Basic ECC
Version in use: 3.15.3.1 Basic ECC
NSSSSL
Expected minimum version: 3.15.3.1 Basic ECC
Version in use: 3.15.3.1 Basic ECC
NSSUTIL
Expected minimum version: 3.15.3.1
Version in use: 3.15.3.1

hello Sonoko, thanks for reporting with your troubleshooting information - i think i don't fully understand the problem yet. do you get a sort of error message when you're trying to use firefox or does the presumed lack of .NET in firefox cause any particular other issues?

See also:

• http://msdn.microsoft.com/en-us/vstudio/cc716877%28v=vs.102%29

philipp wrote: "hello Sonoko, thanks for reporting with your troubleshooting information - i think i don't fully understand the problem yet. do you get a sort of error message when you're trying to use firefox or does the presumed lack of .NET in firefox cause any particular other issues? "

Yes, my HP Smart Print in unable to work and freezes up.

@cor-el Sorry, that link didn't help.

https://addons.mozilla.org/en-US/firefox/addon/microsoft-net-framework-assist/

I found the problem and the solution (above link). Thanks so much philipp and cor-el for your time.