Unable to upload sketches to aduino Uno on Windows 7-Serial port already in use

hi all

it has been 2 days since baught arduino uno , until yesterday tested several things blinking , fading led , worked fine. yesterday when following tutorial involving coding follows couldn't upload more sketch board.

code: [select]

int sensepin = 0;

void setup(){
  analogreference(default);
  serial.begin(9600);
}

void loop(){
  serial.println(analogread(sensepin));
  delay(500);
}

when first compiled , uploaded code expecting serial monitor window come did in tutorial video nothing came up. tried compiling , uploading again. gave error as

code: [select]

processing.app.serialexception: serial port 'com29' in use. try quiting programs may using it.
at processing.app.serial.<init>(serial.java:171)
at processing.app.serial.<init>(serial.java:77)
at processing.app.debug.uploader.flushserialbuffer(uploader.java:77)
at processing.app.debug.avrdudeuploader.uploadviabootloader(avrdudeuploader.java:175)
at processing.app.debug.avrdudeuploader.uploadusingpreferences(avrdudeuploader.java:67)
at processing.app.sketch.upload(sketch.java:1671)
at processing.app.sketch.exportapplet(sketch.java:1627)
at processing.app.sketch.exportapplet(sketch.java:1599)
at processing.app.editor$defaultexporthandler.run(editor.java:2380)
at java.lang.thread.run(thread.java:619)
processing.app.debug.runnerexception: serial port 'com29' in use. try quiting programs may using it.
at processing.app.debug.uploader.flushserialbuffer(uploader.java:101)
at processing.app.debug.avrdudeuploader.uploadviabootloader(avrdudeuploader.java:175)
at processing.app.debug.avrdudeuploader.uploadusingpreferences(avrdudeuploader.java:67)
at processing.app.sketch.upload(sketch.java:1671)
at processing.app.sketch.exportapplet(sketch.java:1627)
at processing.app.sketch.exportapplet(sketch.java:1599)
at processing.app.editor$defaultexporthandler.run(editor.java:2380)
at java.lang.thread.run(thread.java:619)


and since then, every time try uploading code error comes. tried several things on internet none of them worked.
additionally earlier before error came, when plugged in board pc, green led lights , yellow led connected pin 13 keep on blinking forever unless upload sketches.
but after problem happened, once connect board pc green led lights before pin13 led stays lighted forever , led shown in attached pic(as think,  1 connected pin tx) keep on blinking twice every second forever.

could board running last code uploaded it(mentioned before) every time connect pc , since involves sending data pc port becomes unavailable?
if clearing , reprogramming chip using arduino fix problem? or there other simpler way?

one more thing
today noticed when turn pc on,  connect arduino uno , try uploading sketch first time, error follows coming , there on every time try uploading previous error coming.

code: [select]

processing.app.serialexception: error opening serial port 'com29'.
at processing.app.serial.<init>(serial.java:178)
at processing.app.serial.<init>(serial.java:77)
at processing.app.debug.uploader.flushserialbuffer(uploader.java:77)
at processing.app.debug.avrdudeuploader.uploadviabootloader(avrdudeuploader.java:175)
at processing.app.debug.avrdudeuploader.uploadusingpreferences(avrdudeuploader.java:67)
at processing.app.sketch.upload(sketch.java:1671)
at processing.app.sketch.exportapplet(sketch.java:1627)
at processing.app.sketch.exportapplet(sketch.java:1599)
at processing.app.editor$defaultexporthandler.run(editor.java:2380)
at java.lang.thread.run(thread.java:619)
caused by: gnu.io.unsupportedcommoperationexception: invalid parameter
at gnu.io.rxtxport.setserialportparams(rxtxport.java:171)
at processing.app.serial.<init>(serial.java:163)
... 9 more
processing.app.debug.runnerexception: error opening serial port 'com29'.
at processing.app.debug.uploader.flushserialbuffer(uploader.java:101)
at processing.app.debug.avrdudeuploader.uploadviabootloader(avrdudeuploader.java:175)
at processing.app.debug.avrdudeuploader.uploadusingpreferences(avrdudeuploader.java:67)
at processing.app.sketch.upload(sketch.java:1671)
at processing.app.sketch.exportapplet(sketch.java:1627)
at processing.app.sketch.exportapplet(sketch.java:1599)
at processing.app.editor$defaultexporthandler.run(editor.java:2380)
at java.lang.thread.run(thread.java:619)

when connected board appears name of com port in device manager there doesn't seem have problem. when plug board pc doesnot have arduino uno drivers installed before, after installing drivers, device properties window says device cannot start.

can please me?

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