Unprotect Sierra   by Independent (IND)

This procedure will enable you to unprotect the following Sierra On-Line's games: KING'S QUEST III SPACE QUEST HELICOPTER LEISURE SUIT LARRY THEXDER The procedure is based on an unprotect procedure for KING'S QUEST III, by an unknown author. There are three files included in this ARC package: 1. SIERRA.DOC - This file 2. SIERRA.DAT - Supplementary file needed during DEBUG session. 3. LARRY.DAT - Supplementary file needer during DEBUG session. SIERRA.DAT was originally named KQ3MERG.DAT, but has been renamed since it is usable in other Sierra games. The procedure is relatively simple: 1) Put a blank, formatted diskette in drive B, and the original Disk #1 in drive A, then at the A> prompt, COPY *.* B:. Then put Disk #1 away - you won't need it anymore! 2) Load DEBUG, making sure both SIERRA.COM or HELI.COM (on the backup disk) and SIERRA.DAT or LARRY.DAT (from this package) are both in the current path or on the default drive. 3.a) Use DEBUG to patch SIERRA.COM for SPACE QUEST. -N SIERRA.COM -L -R (Record value of CX register) -N SIERRA.DAT -L 141 -E 395 XXXX:0395 E8.90 52.90 02.90 -N SIERRA.COM -R CX CX 0080 :???? (Enter value of CX you recorded) -W -Q ♀ 3.b) Use DEBUG to patch SIERRA.COM for KING'S QUEST III. -N SIERRA.COM -L -R (Record value of CX register) -N SIERRA.DAT -L 141 -E 3E1 XXXX:03E1 E8.90 52.90 02.90 -N SIERRA.COM -R CX CX 0080 :???? (Enter value of CX you recorded) -W -Q 3.c) Use DEBUG to patch HELI.COM for HELICOPTER. -N HELI.COM -L -R (Record value of CX register) -N SIERRA.DAT -L 141 -E 366 XXXX:0366 E8.90 7D.90 03.90 -N SIERRA.COM -R CX CX 0080 :???? (Enter value of CX you recorded) -W -Q 3.d) Use DEBUG to patch SIERRA.COM for LEISURE SUIT LARRY. -N SIERRA.COM -L -R (Record value of CX register) -N LARRY.DAT -L 141 -E 038D XXXX:038D E8.90 52.90 02.90 -N SIERRA.COM -R CX CX 0080 :???? (Enter value of CX you recorded) -W -Q ♀ 3.e) Use DEBUG to patch THEXDER.COM for THEXDER. -N THEXDER.COM -L -R (Record value of CX register) -N SIERRA.DAT -L 141 -E 034F XXXX:034F E8.90 7D.90 03.90 -N THEXDER.COM -R CX CX 0080 :???? (Enter value of CX you recorded) -W -Q 4) That's all there is to it. This procedure will probably work with any Sierra game that uses the SIERRA.COM game loader. To check, try the following DEBUG session: -N SIERRA.COM -D 100 (You will see a dump of the first part of the file. If the version is 3.0, this patch should work. If not, you can try, but there are no guarantees) -R (Record the value of the CX register) -S 100 ???? E8 52 02 (Replace ???? with the value of the CX register) You're looking for the E85202 string, which is the call to the protection scheme. With luck, DEBUG will report only one find. Replace that location with the 395 in the E 395 command in the procedure above, and do everything else the same. The idea is to NOP around the call. SIERRA.DAT contains some code that is overlaid on a section of SIERRA.COM - I don't know how it works, but it does. Have fun!