This STOP Code error reports list from aumha.org will tell you more about STOP error code 0xC000021A.
Scroll down, nearly to the bottom, to see the information about your STOP code.
If you use Roxio's GoBack, there is a particular link for the 0x21A error that may be caused by GoBack, or one for an IE 6 error, but it doesn't seem as if this is an IE error.
The other link there is to WinXP's resource kit here, but this seems to only apply to WInXP Professional, and you say that your version is XP Home. The resolution of this in XP Pro seems quite messy, involving a parallel install of XP Pro on another HD or partition.
For what it's worth, I hope these are some help to you.
I know there's been other discussions on c000021a errors but I'm suffering with one now that I think is due to the N0v 8, 2005 Hotfix (KB896424). What I have is an Emachine running XP home with SP2 that has run great since I bought it two years ago. Happened to do a reboot this past weekend (11/19/05), got through the splash screen fine, clicked to login to my account, my background came up - but no desktop/icons. It then went to BSOD and gave the c000021a error.
I can log in safe mode no problem (but NOT with network safe mode), and if I leave the machine at the login screen can even access the Shared folder on it from another machine on my home network (this is how I've been able to offload my data from it).
I tried uninstalling the Hotfix manually from a c: prompt but the files to be restored weren't found. Oddly enough this appeared to be the only hotfix available to uninstall and the directory was dated 11/19. I know winlogon.exe was one of the files involved, the other I think was a gdi32.dll (?).
I've tried restoring back to Nov 2 and booting to last good configuration, neither with any luck.
I'm thinking of trying to re-install the Hotfix from Nov 8 from floppy (thinking maybe it didn't fully install before). Safe mode gets me to a full desktop with icons - but of course no network and crappy graphics. Next to last option is trying a repair from OEM CD (if at all possible), or final option, full restore from OEM CD.
Before I do either repair or full restore, I'm writing here to see if anyone may have a simpler, kinder course of action. It appears to be an issue with winlogon, or something similar. It ain't really busted, just can't get to my desktop. Any suggestions or tips would be greatly appreciated.