Hey guy !
I'm have got a N900, it's great, i just used it a few moths ago!
one time i have use it's coppy data from my friend pc. He had scan virus on my device by soft nivira antivirus...
sine that time i can connect my device to pc
i can format or master flash it!
everything in device can not take out! my contacs, my calendal, my video...
when i plug the cable in to usb there are a box in pc screen "One of the USB devices attached to thí computer has manufutioned, and windows does not recogzined it. For assittance in sloving this proplem, click this messenge"

I had setup the conectivity soft of NOKIA with right cable type
i had setup pc suite and ovi soft
and try more pc!
Thank alot !

i don't know how to conect to pc or reset it!

i can't master- flash the N900 !
Any one can tell me please !

I had some difficulties understanding your English but so far I got this

You connected N900 via mass storage mode to copy some content and your friend scanned it with antivirus after that you cant connect N900 via USB at all? Also you have important data on N900 and dont want to reflash it? right?

"One of the USB devices attached to thí computer has manufutioned, and windows does not recogzined it."

This message appears often when you dont safely remove N900 cable when there was an ongoign read/write opertion and now Windows cant recognize it , probably drivers are damaged ....or less likely phone's memory corrupted..anyways u can do two thing

1. Remove all Nokia software from PC , all connectivity drivers, Ovi suite etc...reinstall and try again

2. or you can do a backup on a memory card and format N900, if u dont know how read this wiki

http://wiki.maemo.org/Updating_the_firmware#N900_2

Cheers

Thank you very much!
i try it now!

i can restore some important data to MMC
But i can't flash it
how to flash it with out cable connect?

i had turn off device. press and hold U key !
then conect to pc ! but the pc do not accept this connection!