Dell OEM disks do not require activation.  If the SLP key is missing this means you did not use DELL OEM media OR you are trying to use XP on a system that did not come with XP.   Microsoft DOES NOT provide support for SLP activation or OEM Versions of windows.   "Microsoft feeds synchronization" errors are XP Internet explorer errors and has nothing to do with Activation." XP is end of life End of support AND microsoft has removed the downloads for Service pack 1 and 2 and 3.   Reinstalls of XP require service packs as well as IE8 minimum. Its probably too late to get most of the links below.  XP is no longer supported. I highly recommend you download all 4 gigs of the files below to a flash drive because later on they will no longer be available.  All of the Dell CD's I have have Dotnet 1.1 sp1 on them.  You have to install your dots in order.  CHIPSET Should be FIRST before anything else.  There will be tons of stuff to install if you don't have even with SP3  IE8 being one. DOTNET 1.1 is on the XP CD from dell.  I strongly recommend you download the files onto a flash drive because there is no telling how long these will stay.  It wont let you backtrack.  [URL]   Once you get all that you can install Firefox ESR  [URL]  And Flash 13.269  [URL]  (Released 2/5/2015) .Flash Player 13.0.0.269 (172.56 MB)  Chrome stand alone (You need Version 49  ) newer 50 and up will not install.  [URL]          
Reinstall Window Xp from CD and was unable to login in to Window after activation.  I found a way to login but still show i had 30 days to activate Window.  Call Microsoft and they validate that my product key was good.  File c:\windows\system32\slui.exe is missing and they couldn't help solving my problem. Microsoft feeds synchronization  has encountered a problem and need to be close.  I do i remove this from coming on my screen every 30 seconds,  thanks
Reinstall Window XP- Product Activation