The excessive loading times is probly because you have a lot of services running in the background. To speed things up try using the msconfig utility.
1) click the start menu
2) click run
3) type msconfig > press enter
4) click the startup tab > disable any uneeded items
5) apply changes > restart
As for the screen flickering maybe try defraging your hard drive. Using the disk defrag or if your interested in using third party utilities i would recommend Diskkeeper or O&O defrag.