There are a number of things you need to do. First, never do this again! You can't simpy re-install Exchange Server - it's much too complicated a beast for this.
Find the following files from your original installation: pub.edb, priv.edb, and dir.edb. If you don't have the original DIR.EDB, stop here and contact me for further instructions.
If possible, copy these files to another server before proceeding.
Open a DOS window and switch to the drive and folder containing the priv and pub. Run the following command:
eseutil /mh priv.edb|more (the vertical bar is the pipe symbol, and can be found on the key just above the enter key)
Look for the "State". Hopefully, it will be consistent.
Run the command using pub.edb instead of priv.edb. Do the same thing for the dir.edb. If the dir.edb is in an inconsistent state, you need help from Microsoft. The rest of this posting assumes that all databases are in a CONSISTENT state.
Write down the following info: drive letter where the priv.edb, pub.edb, and dir.edb are located.
Each drive will likely contain the following folders: x:\exchsrvr\dsadata, and x:\exchsrvr\mdbdata. Note the drive letters where these folders contain files named "edb.log". This is the location of your transaction log files.
Open regedit, and navigate to the following point:
hkey_local_machine/system/currentcontrolset/services/msexchangeds/parameters
Look for the entry named "database log files path". Make sure the drive letter in the key matches the drive where you found the edb.chk under the dsadata folder. Make sure the DSA Working Directory is pointing to drive C:.
Move down in the registry to the msexchangeIS/parametersprivate key. Check the path listed for DB Path, and make sure it matches the location of your Priv.edb.
Do the same in the "parameterspublic" key for the Pub.edb.
Move to the ParametersSystem key and make sure the DB Log Path matches where you found the edb.log file in the mdbdata folder.
Make sure the "Working Directory" value is set to drive C:.
Close the registry editor.
In your dsadata and mdbdata folders, MOVE all files starting with edb and ending with .log to a temporary folder. Look on the dsadata and mdbdata folders on all drives (especially C

for files named edb.chk. Rename these files to edb.old. Rename the priv.edb, pub.edb, and dir.edb that were created when you re-installed Exchange to .old.
Start the System Attendant, followed by the Directory Service. If the Directory service starts, attempt to start the Information Store. If everything goes according to plan, the Store will either start, or you will receive a Service Specific Error 1011 (possibly -1011). If you get SSE 1011, open a DOS window, and change the drive and directory to the location of your priv.edb. THIS IS IMPORTANT!!!!!!!!
Run the following command:
C:\exchsrvr\bin\isinteg -patch. WAIT for the results. This can take anywhere from a few seconds to a few hours. If you get a message back that says the store has been successfully updated, start the Information Store service. You are now back in business.
If you are unable to get the server running, let me know where you ran into trouble, and I'll try to help.