Upgrade Recommendations

I am currently running an Intel Celeron 500 Mhz PC with 512 Megs of Ram, 8.4 Gig hard drive, 40x CD-Rom Reader, Creative 12x 10x 32x CD-RW, 2 Meg video Card (I know, crappy), no 3D card n, yeh. If anybody has any good upgrade options for me could you please recommend them to me. I have been told by some computer guy i cold upgrade just the processor to a 1.1 Ghz for $210 Aus dollars installed. I really want a full upgrade though. Thanx 4 Ur Time Pplz