windows reboots after logging in dll errors

I'm assuming by the heading here that there is a Windows problem of some kind with corrupted/missing DLL's but without knowing what you want to do or what you have there it's very hard to offer any help.

Things like the computer type, it's make & Model, the OS in use and the error message/s would be a starting point. Also what you have done here will also be useful.

Col

When your case is about Windows NT version from 4 to 5.2, then read ahead.

If the reboot happens when pressing Alt-Ctl-Del, the problem is possibly in Winlogon process and its .dll in regisry:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

You may be able access registry from network on other computer (without touching the target computer after boot) to fix the problem by replacing value (after copying current value):

GinaDLL=xxxxx.dll
with
GinaDLL=msgina.dll

For this situation has happened with special
keyboard dirvers, VPN software which have changed logon GUI.

br nasta

Some questions;

What DLLs does it refer to?

Have you tried booting into safe mode (Press F8 during boot)?