OP, my advice is to work from the top down. See if everything at the top level is affected. If it is, step down a level.
Look at overall system responsiveness. Are all programs slow, or only IE/Outlook? Are you getting poor responsiveness on all applications, or only on network activity? Is it only internet (ie, external network) activity, or is it affecting communication with other local devices? One way to check this is to use Internet Explorer to access the configuration page on your router/modem. Try copying a file to another computer on your local network.
If it's only the network related items, take the advice to install Firefox or Opera, and try to discover if it's an IE/plugin issue or a system issue. Installing these browsers now as a clean installation without any plugins will give you good information.
If it seems to be either a system-wide issue, or an IE issue, bring up Vista's Task Manager, and tell it to show all user processes...
Then look at the processess tab and see which - if any - is taking up all your CPU time?
If it is an issue with CPU time being soaked up by some process, it may be a DLL that's obscured from you because they're hosted in 'svchost' processes. A program called 'whatsrunning' can show you which DLL's are being hosted in which svchost processes. That can lead you to understanding which DLL is porked or has a porked config file.
During the meanwhilst, your wife will probably have to do the business-critical work on another machine.
In all this, of course, I'm assuming that the previous poster's assessment that your machine is probably clean, is correct.
