HP iPAQ hx2000 Frequently Asked Questions Manual page 19

3. The label containing the Product ID and the Serial Number is
beneath the battery.
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CAUTION: Because most of the applications and data you install on
your iPAQ Pocket PC are held in memory (RAM), you need to reinstall
them if the battery completely discharges or if the battery is removed
from the unit for extended periods of time.
You do not need to reinstall applications and data installed in the
iPAQ File Store folder because they are saved in ROM.
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