[Uralmosti]

I run a generic PC built up around AMD processor (good machine built by my local computer store) running windows XP. Returning from a weeks break away I find a problem has appeared. I've had a similar before, where certain services were prevented from starting on boot-up. Instructions I'd received back then showed me how to bring up the services and manually start, or re-start them - this (back then) fixed the problem and I could carry on. However, this time, it would seem, no matter what I attempt to do, the 'thing' has got my PC and wont lit it go! My McAfee Total Protection is prevented from doing its job, running its real-time scanning, or allowing me to make elective scans (at will)!? Also, it wont allow browsers to load up. I use IE, Firefox, Chrome & Safari. Windows Security Center keeps reporting I dont have Virus protection installed (or running) - McAfee Total Protection reports my PC is 'at-risk' (the Real-Time-Scanning having been disabled!). I click the appropriate buttons to restart the McAfee Anti-Virus Real-Time-Scanning and, for a while, it remains 'ON'. Security Centre shows Virus Protection as 'ON' also. Then, as I click to bring on a browser, the system take on the pace of a snail and becomes all 'Non-responsive'. When it allows I can check certain functions, and check things out with the Task-Manager, but I've tried a number of things and feel now at a bit of a loss to know where to go next. Geeks to Go has helped me before, so I figured if I asked nicely, some well informed Geek out there would pick me up and dust me off! I am typing this up on my Toshiba laptop - it uses the same McAfee Total Protection and licence for Virus and other protections.
I look forward to a suitable reply, Many Thanks,...