Well , you're running a basement bargain PC. 333 may be the top speed of the mobo's memory interface.
Basically all you'll be able to do in the BIOS is look at the settings, as pre-builts ahve locked BIOS.
If you've dropped a gig of RAM in it, it's probably giving you its best right now. If you want better, you'll have to replace your CPU and add a grphics card (if the mobo have a slot for it).
My Rig: SABLE
Antec 300 Illusion / Antec EarthWatts EA650 650W / EVGA GTX 760 2GB
AMD FX 8320 x8 Black Edition / Gelid Tranquillo / MSI 970A-G43
Sandisk Ultra Plus 128GB / Samsung 840 120GB / WD Black 750GB / WD Green 1TB / WD Red 3TB
G.SKILL Ripjaws 2x2GB DDR3 1600 - Crucial Ballistix Tracer 2x2GB DDR3 1600
Win7 Ult 64-bit - Func MS3 Mouse - CM Storm QuickFire Rapid Mech Keyboard
R.I.P. Danny L. Trotter
... 14 Nov 1945 - 4 Sept 2009