Be advised that UMP2 files are up to 1 GB in size. Most WWW browsers are not able to reliably download big files. For error-free downloading of huge files small utility called "wget" is provided here. To use it you need to save "wget.exe" and "download.bat" in same directory and run "download.bat". If for whatever reason download is interrupted (net failure, crash, etc.) it can be resumed by running "download.bat" again. Please make sure to have enough space on disc.
Fast mirror is provided by Putmacher, at

FileSizeWGET linksDirect download
UltimateMappack2 with updates 1,2,3,4,5 included1GB == 1081974803B mirror
HHO 2010 Mappack
This is first half of Update6
128MB == 133933503B mirror
sUk-stronghold Pack
by Imp Hunter - improved sUk-Stronghold1 and brand new sUk-Stronghold2, both with EVAC versions. Tutorial included.
This is second half of Update6
152MB == 158555591B mirror
Only updates 1,2,3,4,5 for UMP2
Download BOTH this and Update6 ONLY if you already have UMP2 without updates
600MB == 610972958B mirror
AvP2 Savior Mod v2.0 by LithFaq and TBBH
Required to play without (no longer existing) Sierra and GameSpy servers
41MB == 42310485B download

Notice: Wget is a free software licensed under GNU General Public License. For more info look here and here.