1GB pendrive gets detected as 970MB only. why? i have windows XP Pro?

This is natural. There is always a slight error. If you dont like it, trade it in... you might get a little more but you will never get a full 1GB

1GB pendrive gets detected as 970MB only. why? i have windows XP Pro?microsoft zune

because the other 30mb are used so that when u plug it in it can be auto recognized and run off of itself.

1GB pendrive gets detected as 970MB only. why? i have windows XP Pro?windows nt internet explorer

Windows XP correctly identified the drive size. Its how drive space is marketed, for instance ill buy a 20gb hard drive but only get tto use around 18~19 gigs of space.
Sizes are never exactly what they say it is, it's a normal occurance for any type of storage, they always round up the real value to market it better, there is nothing you can do about it.
Everything you buy assumes that 1GB = 1,000,000,000 bytes. This is not how the computer interprets things, however. To a computer, 1,024 bytes = 1kB, 1,024KB=1MB, 1,024MB = 1GB, so therefore 1,073,741,824 bytes = 1GB. That is why the actual capacity is less.
It is reserved system space with some system data so that your pendrive will autorun on your computer and it will catalog everything on your pendrive. It is like windows XP on a hard disk. The XP system files take up space on your hard disk.
Hard drives have ALWAYS had less space than the rating because of all the housekeeping functions... the larger the HD the more space that is lost... it has ALWAYS been this way... from the very FIRST 10 Mg. hard drives up to todays monsters.
It is a combination of what the manufacturer considers 1GB to be and what the OS considers 1GB to be. It is also due to needing a "file system" on the device and this takes some space for overhead (file metadata like location, size, date, owner, permissions, etc...). So it is both a measurement and overhead issue.
Not sure about flash memory drives, but hard drive manufacutres measure 1GB as 1000MB, while xp uses 1GB = 1024MB.