Get more RAM. Vista requires at least 2gb to run half way smooth. Uninstall McAfee and install AVG Antivirus. let vista do the firewall work and you should have windows defender for Malware.
Future upgrades should include a video card. An 8400 is fine and dandy, but its low end for graphics. You can get an 8600 pretty cheap now.
<MasterJo> you want pics of me in boxers??? <Rhett>for... research