Check the drive by putting it in another system. If it is ide, you might need an ide adapter. If sata, you can use it on any sata controller. Back up your data or image the drive if it looks normal.
You have probably hosed the system board or at least the bios. If the methods previously described/linked to by garmanma do not allow you to reset the bios to system defaults (pull cmos coin battery with ac unplugged and battery removed, wait for all lights to go out or wait 15 min, replace coin batt and try again) you probably have a serious problem with the board and it may need to be replaced.
This may give you an overview of what the manufacturing mode is used for. It is unlikely to really help.http://support.dell.com/support/topics/glo...mp;toggle=false
Some notes from similar models. (I have a 9100 on my bench now) Dell power supplies of this era have a third wire that is read by the bios to determine if you have a "real" Dell brand power adapter and will refuse to charge the battery. Thus some of the errors you posted may not be real errors as such, but indications that the bios is not able to do its job and clues that the bios or mainboard or both are not readily repairable by end users. If this were a warranty situation, the board would be replaced and the Dell tech would probably set the mfg mode to match the one on the tag inside the bottom cover and a new service tag would be applied to the outside or the tag number set in the bios. (It has varied over the years and I am no longer doing warranty work for anyone.)