Well the Ctrl+A (selectall), Ctrl+Q and Ctrl+Spacebar will certainly clen up loads of mess and let you go through to reapply any styles that are not correct.
However, if the document (or part of) has even been in Word XP, then there will be masses of crap hidden in its structure. If that is the case, you may ber able to remove much of this by (using a copy of the document) saving it in RTF, closing it and opening it and saving back into .doc format. An indication that this has worked is a reduction in file size of the document before and after going through the RTF circle.
However, the only guaranteed solution to getting it really clean and stable again is to convert it into plain text in a text editor such as Notepad and saving it as a .txt document. Then open it in Word and apply all the styles correctly.
Regards: tf1