|"my tv only has an HDMI port"|
Then do as I suggested in response #2 & install a graphics card with HDMI port.
XFX Radeon HD 5450 1GB 64-Bit DDR3 PCI Express Video Card - $15 after rebate
If you haven't upgraded the RAM, here's a possibility:
AllComponents 2GB (2 x 1GB) DDR2 667 - $26
And you might wanna consider upgrading the power supply as well because the stock eMachines units (usually Bestec) suck.
CORSAIR CX430 430W - $20 after rebate