for anyone interested: i have successfully slipstreamed SP2-RC1 (and installed it without trouble) using Barts method http://www.nu2.nu/bootcd/#wxp . Below is an edited procedure taken from Bart's original. Hope it's a little easier to understand. Note that i used an I386 folder without SP1 installed. ie., an original XP Pro CD install Disc sans any Service Pack files.

This will show you how to create a bootable Windows XP Home Edition or Professional installation CD. Optionally you can integrate (slipstream) SP1 or SP2 and add extra files to your CD. The boot catalog and the NT bootstrap loader are hidden just like the original bootable Windows XP CD. Joliet extensions are enabled by default so you can have long filenames on the CD.
Note: This will NOT create a dual-boot XP CD with Home edition and Professional on one CD.

1. BCD installation instructions

Unpack contents of bcd111.zip  to a folder, for example C:\bcd. If you want to be able to run it from a server you should unpack it to a share from where your workstations can run it. You will need to map a drive letter to that share and run bcd using that drive letter.

Copy wnaspi32.dll into BCD's C:\bcd\bin directory.

Unpack the contents of wxp10.zip into the BCD directory C:\bcd.

This Windows XP package contains the Windows XP bootstrap loader (same as Windows 2000) and some other files used to build the CD.

You must copy the i386 folder from your Windows XP installation/setup CD-Rom.
For Windows XP Home Edition copy it to the C:\bcd\cds\wxphome\files\ folder.
For Windows XP Professional copy it to the C:\bcd\cds\wxppro\files\ folder.
Make sure you copy all files and all subdirectories!

If you're Windows XP files are already "slipstreamed" with a service pack you must also copy the win51ic.SPx or win51ip.SPx file.
This will prevent the CD asking "put the SPx CD into drive A:" during install.

The location of the i386 folder may differ, for example when you have a dual boot MSDN cd-rom it will be in \%lang%\winxp\%edition%, where %lang% is your language, like "ENGLISH", "GERMAN" and %edition% is "Home" or "Pro". Other CD's may have it just in the root or in some other location.

Optionally you can also copy the following files (not needed for bootable CD installation):
autorun.inf
readme.htm
setup.exe

If you have a Windows XP CD from MSDN...
Edit the file i386\txtsetup.sif
section [SetupData], and change the setup source path, it should read: SetupSourcePath = "\"

You can apply SP1 or SP2 to this installation (integrated installation). So that you have an installation CD-ROM with the service pack built in.
Apply service pack to your files using the "-s" option (you must supply full path).

Eg.,for Windows XP Home edition: <location of file> \xpsp1_en_x86.exe -s:C:\bcd\cds\wxphome\files\
Eg.,for Windows XP Professional: <location of file> \xpsp1_en_x86.exe -s:C:\bcd\cds\wxppro\files\

Notes:

The Service Pack file can have another name, like xpsp1_nl_x86.exe for Dutch language.
The xpsp1_en_x86.exe can only be run on a Windows 2000 or XP PC!
You should now have a win51ic.sp1 or win51ip.sp1 file in the files directory. Check this, to prevent the CD asking "put the SP1 CD into drive A:" during install.

All other files and folders you want on the CD-Rom must also be added to the files directory, these files will not be integrated in the Windows XP installation, they're just parked there. Things you could add are: latest patches, internet explorer, directx.

Add your files to:
For Windows XP Home edition: C:\bcd\cds\wxphome\files\
For Windows XP Professional: C:\bcd\cds\wxppro\files\

Now insert a blank CD into your CD drive

Open a command prompt and run:
For Windows XP Home edition:C:\bcd\bcd wxphome
For Windows XP Professional:C:\bcd\bcd wxppro

This will build the (bootable) ISO image and burn it to the CD.