Vista - Problems with Vista Home Premium 64bit

I recieved an Acer Aspire G7200 Predator (see sats below) for my 21st roughly 3 weeks ago and everything was fine for the first week, it was fast, responsive and games installed within seconds.
Since the system started installing windows updates i've had all sorts of problems. My computer has become sluggish at start up despite disabling all unnnecessary programs. It also seems to have trouble running installation disks, the process is painfully slow and the desktop freezes if you try to run anything at the same time. which was never a problem before...
Even more frustrating is that i bought a copy of Corel VideoStudio Pro X2 (completely vista compatible!) and it freezes half way through installing the installation wizard... =/ Then i get the following error code: "1670: Unable to load module K:\ISSetup.dll, Error code:999" and then the program closes...

I really hope someone can help me with this because i'm at my witts end!

Syst mod: Acer Aspire G7200 Predator
OS: Windows Vista Home Premium x64
CPU: AMD Phenom 98502 Quad-core ~ 2.5GHz
RAM: 4GB DDR II
HDD: 150GB (10kRPM), 640GB
VGA: 2x ATI Radeon HD 4950 1GB