This will try to agregate several tips about install problems & workarounds (if possible/available)
AGPGART / Dell Optiplex 320
If you have a NIC like this one:
Linux agpgart interface v0.100 (c) Dave Jones
Or problems with boot on a Dell Optiplex 320 with integrated ATi graphics you could try to add this boot option
when installing from the CD.
If you have a new motherboard, you should try to use SME8 (in Beta6) to get better chances of SME support all your hardware.
In special one section you should take a look is how SATA is configurated. The default in some BIOS is IDE mode ( a backward compatible mode who permit SATA to be "translated"as IDE so old operating system can be used (SME7 in this case) even if they do no support SATA HDDs.
For performance reasons, you ALLWAYS should use AHCI mode or something like Native mode.
Atheros / Attansic
See bug #6593: http://bugs.contribs.org/show_bug.cgi?id=6593