twister

I went to power on my axim this morning and it would not come on.I assumed the battery may have died so I replaced it and when I powered it on it did a hard reset on its own.I put the battery it originally would not power on with back in and it reads 80%.Does anyone know what may have caused my hard reset?????I have a free replacement contract with Dell for this unit which expires in september and would like to send it now if it's about to fail.

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Axim x5 advance 400mhz
Mugen 3800mha Battery
Mugen 2000mha Battery
512mb Kingston SD
1gb Kingston CF
Piel Frama Case
Rhinoskin Titanium Case