By mobi battery I mean the small battery which sits in its cradle on the motherboard itself. CMOS battery, yes. Do not just reset the CMOS battery: replace it.
It's cheap enough at Radio Shack. (Or your equivalent in the UK)
The CD/DVD. I'm writing this at work (tsk! tsk! bad boy!) on an HP NC8000 craptop (laptop).
(I believe the craptop you are working on is also an HP bestowed one?) I have a similar problem to yours e ie, CD's work fine - to boot from - but DVDs boot occasionally. I believe, but I'm not certain, that a BIOS update might fix that OR
the CD/DVD drive needs to be replaced.
In essence, you not only have software issues - which I assume you're still working on - but hardware as well. I do, however, concur with others in that unless you
get Vista running properly soon, I would start all over again. During the SP2 "upgrade" the process will patch some files, delete other files and add new ones. Since this process was interrupted the system is in a rather precarious state, to say the least.
If the DVD drive won't install properly can you get your hands on an external USB drive?