Softpaqs recommended 
by Compaq and the AeroFAQ:

As far as I understand the purpose of the following two softpaqs, SP2158 (setport) is the utility to force the LPT-Port into a special mode/configuration. 
The other one, SP1630, contains all drivers needed for these modes (normal, EPP, ECP or bidirectional).

Unfortunately no member of the aero mailing list ever seemed to have success with the installation of these LPT-Drivers.

In the Manual "Beyond setup" Compaq describes the LPT-port as "enhanced parallel port" (page 2-5). 
Windows 95 has configured the LPT-port automatically as ECP.So it seems to me, no extra driver is needed for that OS.

SP2158.EXE
ftp://ftp.compaq.com/pub/softpaq/sp2001-2500/sp2158.exe
ftp://ftp.compaq.com/pub/softpaq/sp2001-2500/sp2158.txt
41K
SOFTPAQ NUMBER: SP2158
PART NUMBER: N/A
FILE NAME: SETPORT.EXE
TITLE: Laptop Parallel Port Configuration Utility
VERSION: 1.0
LANGUAGE: English
CATEGORY: Software Solutions/Laptop
PRODUCTS AFFECTED: Contura Aero, LTE Elite, Contura 400 Series, LTE 5000 Series, Armada 1100 Series, and Armada 4100 Series
OPERATING SYSTEM: DOS, Windows 3.1, Windows 95
EFFECTIVE DATE: 24 Sept 1996
ELECTRONIC DISTRIBUTION ALLOWED: Yes
DESCRIPTION: Contains the SETPORT utility, which allows a user to configure the parallel port in the following modes on the Compaq laptop products mentioned above that support these modes:

- Standard unidirectional mode
- Bidirectional mode
- EPP mode
- ECP mode

SETPORT uses the IEEE 1284 BIOS specification.


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SP1630.EXE
ftp://ftp.compaq.com/pub/softpaq/sp1501-2000/sp1630.exe
ftp://ftp.compaq.com/pub/softpaq/sp1501-2000/sp1630.txt
42K
Softpaq Solution: SP1630
File Name: EPPBIOS.SYS
Title: IEEE 1284 EPP BIOS Draft Revision 3 Support for Laptops
Version: 2.0
CATEGORY: Drivers/Laptops
EFFECTIVE DATE: 12 Apr 1996
PRODUCTS AFFECTED: LTE Elite, Contura 400 Family, and Contura Aero
OPERATING SYSTEM: MS-DOS 6.0 or greater
SYSTEM CONFIGURATION: MS-DOS with a parallel port device that supports
IEEE 1284 EPP BIOS Draft Revision 3
SUPERSEDES: SP1147
DESCRIPTION: Contains four driver files which will load IEEE 1284 EPP (Draft Rev. 3) Bios Support on Compaq LTE Elite, Contura 400 Family, or Contura Aero laptops. This support is needed when an EPP device requiring functions specified by IEEE 1284 is connected to one of the affected laptop products. EPPSLCOM.SYS is known to fix Conner Tape Stor tape backup systems that run off the parallel port.



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Other Softpaqs:

Although perhaps newer, older or originally not intended for the Aero, you might want to try these softpaqs because of localizations, extra features or other purposes. 

I never tried out any of these...

SP1837.EXE
ftp://ftp.compaq.com/pub/softpaq/sp1501-2000/SP1837.EXE
ftp://ftp.compaq.com/pub/softpaq/sp1501-2000/SP1837.txt
37,3KB
Softpaq Solution:  SP1837
File Name:  SETECP.EXE
Title:  Fix EPP/ECP devices on LTE 5000
CATEGORY:  Software Solutions / Laptops
EFFECTIVE DATE:  07 May 1996
PRODUCTS AFFECTED:  LTE 5000 Family
OPERATING SYSTEM:  MS-DOS 6.0 or greater, Windows 3.1, or Windows 95 
SYSTEM CONFIGURATION:  Parallel port devices that require EPP or ECP mode support 
DESCRIPTION:  SETECP.EXE is a utility for laptops in the LTE 5000 Family that enables the registers used for certain parallel port devices that require EPP mode (Enhanced Parallel Port) or ECP mode (Extended Capabilities Parallel Port).  The utility does not force the parallel port into ECP mode.  It enables access to the registers required to place the port in EPP or ECP mode.


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SP1147.EXE
ftp://ftp.compaq.com/pub/softpaq/sp1001-1500/SP1147.EXE
ftp://ftp.compaq.com/pub/softpaq/sp1001-1500/SP1147.txt
37,6KB
Softpaq Solution: SP1147
File Name: EPPBIOS.SYS
Title: IEEE 1284 EPP BIOS Draft Revision 3 Support For Contura Aero and Contura 400 Family
Version: 1.5
CATEGORY: Drivers / Miscellaneous
EFFECTIVITY DATE: 02-23-95
PRODUCTS AFFECTED: Contura Aero, Contura 400 Family
OPERATING SYSTEM: MS-DOS 5.0 or greater
SYSTEM CONFIGURATION: MS-DOS with a parallel port adapter that supports IEEE 1284 EPP BIOS Draft Revision 3.
SUPERCEDES: SP0937
DESCRIPTION: EPPBIOS.SYS is a driver which will load IEEE 1284 EPP (Draft Rev. 3) Bios Support on Compaq Contura Aero or Contura 400 Family machines. IEEE 1284 EPP (Draft Rev. 3) Bios support is needed for adapters to use IEEE 1284 specified EPP functions.

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SP0937.ZIP
ftp://ftp.compaq.com/pub/softpaq/sp0501-1000/SP0937.ZIP
11,9KB
Softpaq Solution: SP0937
File Name:EPPBIOS.SYS
Title:IEEE 1284 EPP BIOS Draft Revision 3 Support For Contura Aero and Contura 400 Family.
Version: 1.4
CATEGORY:  Driver
EFFECTIVITY DATE:  09-15-94
PRODUCTS AFFECTED:  Contura Aero, Contura 400 Family
OPERATING SYSTEM:  MS-DOS 5.0 or greater
SYSTEM CONFIGURATION: MS-DOS with a parallel port adapter that supports IEEE 1284 EPP BIOS Draft Revision 3.
SUPERCEDES:  SP0935.EXE
DESCRIPTION:  EPPBIOS.SYS is a driver which will load IEEE 1284 EPP (Draft Rev. 3) Bios Support on Compaq Contura Aero or Contura 400 Family machines. IEEE 1284 EPP (Draft Rev. 3) Bios support is needed for adapters to use IEEE 1284 specified EPP functions.



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SP0935.ZIP
ftp://ftp.compaq.com/pub/softpaq/sp0501-1000/SP0935.ZIP
11,9KB
Softpaq Solution:  SP0935
File Name: EPPBIOS.SYS
Title:  IEEE 1284 EPP BIOS Draft Revision 3 Support For Contura Aero and Contura 400 Family.
Supersedes Softpaq SP0889.EXE. (Version and Language are not applicable here)
CATEGORY:  Driver
EFFECTIVITY DATE:  09-13-94 (does not need to match the release date)
PRODUCTS AFFECTED:  Contura Aero, Contura 400 Family
OPERATING SYSTEM:  MS-DOS 5.0 or greater
SYSTEM CONFIGURATION: MS-DOS with a parallel port adapter that supports IEEE 1284 EPP BIOS Draft Revision 3.
INTRODUCTION: EPPBIOS.SYS is a driver which will load IEEE 1284 EPP (Draft Rev. 3) Bios Support on Compaq Contura Aero or Contura 400 Family machines. IEEE 1284 EPP (Draft Rev. 3) Bios support is needed for adapters to use IEEE 1284 specified EPP functions.



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SP0889.zip
ftp://ftp.compaq.com/pub/softpaq/sp0501-1000/SP0889.ZIP
11,5KB
EPPBIOS.SYS
A driver which will load IEEE 1284 EPP Bios Support on
Compaq Contura Aero machines.  IEEE 1284 EPP Bios support is needed
for adapters to use IEEE 1284 specified EPP functions.