Arduino IDE doesn't start

Hello,
recently, i downloaded the arduino IDE and it worked perfectly...
But, a day, I download 1.6.4 version and when I tried to start it, the start icon appeared, it print "loading configuration", "initializeing packages" and... it crashed. I tried 3/4 times again but the same thing at each try. I thank "it's a bug with the 1.6.4" so I uninstalled it and I install again the 1.6.3 (who worked perfectly) and the same thing happened ! my laptop is an old dell with Windows XP. The processor is a 1.6Ghz 500mo of ram Pentium Intel.
Can you help me ?

Sure. Can you please try starting the IDE from the command prompt: use arduino_debug.exe. Before terminating, it will print an error message. Please paste it here

Loading configuration...
Initializing packages...
com.fasterxml.jackson.core.JsonParseException: Unexpected character ('<' (code 60)): expected a valid value (number, String, array, object, 'true', 'false' or 'null')
at [Source: java.io.FileInputStream@17f23d9; line: 1, column: 2]
       at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1369)
       at com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:532)
       at com.fasterxml.jackson.core.base.ParserMinimalBase._reportUnexpectedChar(ParserMinimalBase.java:453)
       at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._handleUnexpectedValue(UTF8StreamJsonParser.java:2278)
       at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._nextTokenNotInObject(UTF8StreamJsonParser.java:779)
       at com.fasterxml.jackson.core.json.UTF8StreamJsonParser.nextToken(UTF8StreamJsonParser.java:665)
       at com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:2926)
       at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2873)
       at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2080)
       at cc.arduino.contributions.libraries.LibrariesIndexer.parseIndex(LibrariesIndexer.java:79)
       at cc.arduino.contributions.libraries.LibrariesIndexer.parseIndex(LibrariesIndexer.java:68)
       at processing.app.BaseNoGui.initPackages(BaseNoGui.java:625)
       at processing.app.Base.<init>(Base.java:256)
       at processing.app.Base.guardedMain(Base.java:198)
       at processing.app.Base.main(Base.java:113)

It's all the error message.

It looks like the download json file is corrupted. Please open folder %APPDATA%\Arduino15 and delete all .json files

Alleluia :smiley:
Thanks you very much for your help