File too big to be saved

I'm trying to merge 20 years worth of newsletters that are in individual pdfs into a single searchable pdf. 548 files, 5298 pages, 3.87 GB.

Using a Dell PC, Windows XP with Service Pack 3 and all updates. Pentium 4 3.62 GB Ram. Hard drive is 465GB with 358GB free. Using current Acrobat Pro 9.3.3. Also have Acrobat Reader and Elements on my machine.

No problem merging the files as the single merged file shows up on the screen with all the individual files bookmarked just as I want. It won't save, however. "The document could not be saved. This file is too big for the current operation." Tried "Save" and "Save As", tried saving as the default Binder1 and also renaming and directing the file to another folder. In looking at the document properties I can see that the single combined file is named A9R3CDB.tmp and is in a documents and settings folder. Document properties also says that the PDF is version 6 (Acrobat 7.x) and that the file size is 3.56KB, no security, everything is allowed.

Nothing I have tried will allow me to seve this file even though there is plenty of room on the drive. Hit "repair" for Adobe 9.3.3 and finally removed it and reinstalled with the same results. I can save about 1/3 of the files into each of 3 different folders, but they won't combine giving the same file too big error. Can optimize each of the folders and combine them into one document, but then there are top level bookmarks and I just want the 548 file bookmarks.

Any suggestions are appreciated. I'm a novice with Acrobat Pro.