如何将Ubuntu8.04的usb设置恢复初始化状态！

我的Ubuntu8.04前几天更改设置后不能挂载U盘了。郁闷的是我忘记我更改的是什么！
各位有谁知道如何将Ubuntu8.04的usb配置恢复初始化状态？？？
我的U盘挂载后弹出了一个提示窗口（见附件）
下面是输入dmesg |tail 后的信息：
xtay@xtay-desktop:~$]xtay@xtay-desktop:~$dmesg |tail
[ 1527.865072] sd 7:0:0:0: [sdb] Assuming drive cache: write through
[ 1527.866479] sd 7:0:0:0: [sdb] 7897088 512-byte hardware sectors (4043 MB)
[ 1527.866718] sd 7:0:0:0: [sdb] Write Protect is off
[ 1527.866721] sd 7:0:0:0: [sdb] Mode Sense: 00 00 00 00
[ 1527.866722] sd 7:0:0:0: [sdb] Assuming drive cache: write through
[ 1527.866726] sdb: unknown partition table
[ 1527.917333] sd 7:0:0:0: [sdb] Attached SCSI removable disk
[ 1527.917367] sd 7:0:0:0: Attached scsi generic sg1 type 0
[ 1528.083209] UDF-fs: No VRS found
[ 1528.101391] ISOFS: Unable to identify CD-ROM format.

如果知道怎样将整个Ubuntu系统恢复到初始状态也可以。本人实在不想重装。