My files are dated as follows.

C:\Program Files\Alwil Software\Avast4\Setup|Inf

AavmKer4.inf 2KB 17/10/2002 18:06
Aavmker4.sys 13KB 11/09/2003 17:02
AswMon2.inf 2KB 16/10/2002 09:46
aswMon2.sys 47KB 11/09/2003 11:06
aswMon.sys 50KB 11/09/2003 11:06

C:\WINDOWS\system32\drivers

aavmker.sys 13KB 03/07/2003 13:58
aswmon2.sys 44KB 03/07/2003 14:01
aswmon.sys 46KB 03/07/2003 14:01

I haven’t noticed any problems (apart from Shadow copy backup mentioned elsewhere).