Please help me out with sitemaps and 404's much appreciated!

Please note: Im very new with forums and how the sitemaps and seo on them work, im doing my best but cant get to understand some simple things you might know the answer to the same second you read them.

1. I seem to have 2 sitemaps at the moment, although i dont think i ever made 2. Im not sure where the second one came from and why it is there, and if i need it or should remove it. I didnt install sitemapgenerator yet because i simply dont know how and i dont want to wreck anything. Here is the log from google webmaster tools:

Bestandsnaam Status Indeling Gedownload URL's verzonden URL's geïndexeerd sitemap_1.xml.gz Sitemap 5 feb. 2010 339 17 sitemap_index.xml.gz Sitemap-index 5 feb. 2010 339 17
As you can see, 2 sitemaps, both seem to be identical in what urls are indexed.


2. While checking google webmaster tools i saw that there where crawlerrors. Here is a small list of the errors its given me:

http://www.3dmovieforum.com/forumdisplay.php?1-3D-Movie-Main-Forum 404 (Niet gevonden) 12 pagina's 29 jan. 2010 http://www.3dmovieforum.com/forumdisplay.php?11-Post-something-about-yourself 404 (Niet gevonden) 12 pagina's 29 jan. 2010 http://www.3dmovieforum.com/forumdisplay.php?12-3d-movie-glasses 404 (Niet gevonden) 12 pagina's 29 jan. 2010
I changed one of the default settings on how the urls should look last week, is this why this is happening?
What should i do to change this? Is it bad?

Thanks a lot, all help appreciated!

1) This is normal. sitemap_index is just that-- an index or table of contents of all your sitemap files. When you have a lot of urls, you will start generating sitemap_2.xml.gz and so on, and all will be linked from the index file.
You ONLY want to submit sitemap_index.xml.gz

2) Those are old vbulletin 'friendly' urls. vbSEO only re-directs vbulletin STANDARD urls (ie, forumdisplay.php?f=1)
These old URLs will eventually drop out of the index, replaced with your actual URLs.