I can downlaod android market in my phone lg gt 540

my wild guess it is a cell phone, ?
it is not a relic GATEway PC from 1998 to 2013.

its phone or notepad (unstated model or maker)
Microsoft phone,.
Samsung 504. what is it .
notebook HP 540
Gateway FX540XG from 20 years ago?
Samsung Rant SPH-M540
LG phone -UN540-wine-4
MS
Windows 10 Mobile is being made available to supported smartphones running Windows Phone 8.1. Phones and devices that can upgrade to Windows 10 are Lumia Icon, 1520, 930, 640, 640XL, 730, 735, 830, 532, 535, 540, 635 1GB, 636 1GB, 638 1GB, 430, 435, BLU Win HD w510u, BLU Win HD LTE x150q and MCJ Madosma Q5011.
MICROSOFT LUMIA 540

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GT 540 dose not support On Screen Phone (OSP). Please check the GT 540 Manual

The easiest way to change the theme or look of the LG Optimus (or any Android phone for that matter) is to download a new launcher. The Launcher is like the desktop for Android, where you can place widgets and app icons. There are different Launcher's available to download from the Android Market, and some of them can be themed and dramatically change the look of your phone. There are multiple good ones that can be themed. Just go to the Android Market, search for ADW, OpenHome, GO Launcher EX, just to name a few that can be themed.
Once you install the new Launcher, when you hit "home" it will bring up options to choose which Launcher you want to use. Don't select "use as default" until you're sure you want to settle with one of them. (*if you do select use as default, and then want to change again, see the note at the end of this)
If you go back to the Android market, and search for ADW themes, OpenHome themes, etc., you should see quite a long list of various themes for each launcher. Install one you want to try, then hit home. You'll need to apply the theme in the Launcher's settings, which is normally accessed by (from the home screen) hitting the menu button, and then "preferences" or "adw settings" (if you're using ADW). From there, depending on the Launcher you're using, find the section that has to do with "Themes" or "UI". From there, you should be able to select and apply the theme you just downloaded and installed. It can't hurt to download a few if you want to test a few.
Changing Launchers is a great way to change the look and feel of you're phone, as a lot of them run much smoother than the Launcher that comes default on the phone.
*If you set a Launcher as default, but want to change it... the easiest option is to download "Home Switcher for Froyo" from the Android Market, and use that to change between Launchers. The longer was is to go into Settings -> Applications -> Manage Applications, find the Launcher you're using, click on it, and select "clear defaults". Then when you hit the "home" button, it should bring up your options again.

When you reset to factory settings, you have to re-configure the Gmail account for the phone.
Make sure you entered a valid Gmail account in the:
Settings -> Account menu.
Also, if you're using a data plan to access the Android Market, verify that you have
Data Enabled on the Settings -> Wireless & Network Settings -> Mobile Network
Settings.

Hope it helps!

Hi, To get the GPRS setting please call your service provider(customer care). They will send you the GPRS setting.After you recieve please save the settings to your phone and make it as default setting.You can start browsing internet on your LG GT 540.

Good Luck. Thanks for using FixYa.