configuration register settings

config-register in global configuration mode
confreg in rommon mode

1. 0x2100 -always go to rommon mode and in rommon if use                        confreg 0x2100 will again be there
2. 0x2142 -bypass the configuration and enter setup mode
3. 0x2102 - normal boot
4. 0x2101 - boots to mini-IOS in ROM