Configmgr/SCCM, Abort PXE issue when attempting rebuilding a PC (re-run a TaskSequence)

Sometimes when attempting to re-image a system you can sometimes be greeted with an abortPXE error. This can even happen after you delete the record from SCCM. What's happening is the WDS/PXE service can be holding onto the record until the cache expires... this cache can sometimes take a long time to expire.

lucky for us since SCCM 2007 SP/2 We've been able to set the cache expiry from the registry.

On a x86 machine
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS\PXEOn a x64 machine the registry key is under WOW6432NodeHKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\SMS\PXECreate a new DWORD value CacheExpire, and set the desired value in seconds. For example, if you prefer the cache expired in 2 minutes, set the value to 120. If the value is set to 0, then the default 60 minutes value is used.
Note: Setting the value in CacheExpire is only supported in ConfigMgr 2007 SP2.

for more information see

http://blogs.technet.com/b/configmgrteam/archive/2010/05/27/pxe-cache-expire-behavior-in-configuration-manager-2007-sp1-and-sp2.aspx

Notes:
I found this can also happen if you delete the record from the system and the target computer is still on and operating before you shut it down. the client sends an update to SCCM before you shut it down.