Altho Djago160 has many thanks and so on, I took the liberty to scan the file and here's the results:
This link of the file taken from his/her siggy:
Kapersky.com
Scanned file: 3Ds Max 5&7 C3 plugin.rar
3Ds Max 5&7 C3 plugin.rar/C3 Editor/5.0/C3_CORE_DLL.dll - OK
3Ds Max 5&7 C3 plugin.rar/C3 Editor/5.0/C3_Exp.dle - OK
3Ds Max 5&7 C3 plugin.rar/C3 Editor/7.0/C3_CORE_DLL.dll - OK
3Ds Max 5&7 C3 plugin.rar/C3 Editor/7.0/C3_Exp.dle - OK
3Ds Max 5&7 C3 plugin.rar/C3 Editor/KeyTools.ms - OK
3Ds Max 5&7 C3 plugin.rar/C3 Editor/KeyTools_cn.ms - OK

3Ds Max 5&7 C3 plugin.rar/C3 Editor/5.0/C3_CORE_DLL.dll clear
3Ds Max 5&7 C3 plugin.rar/C3 Editor/5.0/C3_Exp.dle clear
3Ds Max 5&7 C3 plugin.rar/C3 Editor/7.0/C3_CORE_DLL.dll clear
3Ds Max 5&7 C3 plugin.rar/C3 Editor/7.0/C3_Exp.dle clear
3Ds Max 5&7 C3 plugin.rar/C3 Editor/KeyTools.ms clear
3Ds Max 5&7 C3 plugin.rar/C3 Editor/KeyTools_cn.ms clear
3Ds Max 5&7 C3 plugin.rar clear

Arcavir 2009-05-11 Found nothing
Fsecure 2009-05-12 Found nothing
Avast 2009-05-11 Found nothing
Ikarus 2009-05-12 Found nothing
AVG 2009-05-11 Found nothing
kapersky 2009-05-12 Found nothing
Antivir 2009-05-12 Found nothing
NOD32 2009-05-11 Found nothing
Bitdefender 2009-05-12 Found nothing
Norman 2009-05-11 Found nothing
Clam AV 2009-05-12 Found nothing
Panda 2009-05-12 Found nothing
CP Secure 2009-05-12 Found nothing
Quick heal 2009-05-12 Found nothing
DR Web 2009-05-12 Found nothing
Sophos 2009-05-11 Found nothing
FProt 2009-05-11 Found nothing
VBA32 2009-05-11 Found nothing
So it seems clean. I know I ain't a huge user of this forum, so scan it by yourself, if you see it necessary, but could some1 with knowledge of 3dmodelling test this out?