Hello rockvillegirl,

this "AVGIDSEH.SYS" error after computer start up has been already discussed in these threads:

AVG 2011 Update - AVGIDSH.SYS Crash on reboot
AVG 2011 avgidsh.sys Windows XP

From my personal experiences of last reports about AVGIDSEH.SYS, the culprit is with a driver (or process) after, which will be never showed. I have few confirmations the hard drive check (checkdisk) from Windows XP Recovery Console has solved the issue.

Could you please check the affected hard drive?

Did you try to create the USB medium again? Is possible to create CD version?

Thank you