1 No 3rd party DriverPack are supported for BartPE. None, zip, nada, zero...

2 mass storage drivers can not be added from a third party pack.
   Well they can, but you won't get textmode support only PnP support.
   If your primary drive requires the driver that is in the 3rd party DriverPack it will not appear.
   This is true of BartPE and a normal slipstream.
   Again, an F6 driver wont work from a 3rd party DriverPack...
   BartPE uses the text mode drivers. (the F6 driver)

the best thing for you to do is to [REQ]uest the drivers be added.
We like to add drivers... that is what we do
Requesters are imortant to us and a REQ identifiys you as a person who can test that a certain driver was added correctly!
as Jaak says 'helping us to help you!'

your drivers must be in the mass storage pack and they have to be added very carefully.
Mass Storage is one of the most difficult packs. To get it right anyway. any idiot could stuff one in there but to make it not crash the system afterwards is another story

In Each of the respective forums (LAN and MASS) create a new thread,
use a title like this [REQ] Promise STAT300 TX4
post your HWIDs and a link to where the team can get to the drivers (the OEM source)
And we will get those added for you

i updated your post per 'Read BEFORE you post' in my signature

ANSWER: 3rd party DriverPack's are not supported for the BartPE platform

My 3rdparty dp dir has only the 3rd_party.inf file after I slipstream.
Here is my setup:
Base 809RC1
Other packs used:
DP_LAN_wnt5_x86-32_8053.7z
DP_MassStorage_wnt5_x86-32_805.7z
DP_WLAN_wnt5_x86-32_806.7z

My zipped file:
DP_MTS_wnt5_x86-32_08.11.27.7z

Here is my 3rdparty zip
D
D\3
D\3\M
D\3\W
D\3\M\DontGo.sys
D\3\M\ULSATA2.CAT
D\3\M\ulsata2.inf
D\3\M\ulsata2.sys
D\3\M\ulutil2.dll
D\3\W\athw.sys
D\3\W\athwx.sys
D\3\W\netathw.cat
D\3\W\netathw.inf
D\3\W\netathwx.cat
D\3\W\netathwx.inf

it is for:
Promise STAT300 TX4 PCI\VEN_105A&DEV_3D17&SUBSYS_3D17105A&REV_02\3&267A616A&0&58
Atheros 5006 PCI\VEN_168C&DEV_001C&SUBSYS_139C10CF&REV_01\4&2803E7C1&0&00E2

I look in the regular directories and they have the nt5 directory. Am I missing something?
I'm using this for a BartPE CD and I cant get these 2 drivers to work.

Thanks
Mark