There is not yet a way to upload files or applications via the USB cable to the Sanyo 5300 or Sanyo 8100 i know off.
Besides going through the Sprint service to buy and upload ring tones, screen savers or other applications there are some web sites that let you upload anything you like to your phone.
All you need is to create an account on those sites and upload to a an online folder what you want to upload to your phone. You connect with your phone to the site and bingo you can install ring tones, games whatever on your own terms.
Here are two sites that offer this service:
3G Vision Correction - They charge a modest $10/year for an account.
3G Upload - They are still Free but like to get donations
SprintPCSRocks.comGreat Site that lists the best Ringers, Screensavers, etc. sites.
Another useful site is the Sprint Users Forum, lots of sprint vision fanatics there to help.
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