You only have a AGP slot. Heres your motherboards spec.
http://www.emachines.com/support/product_support.html?cat=Desktops&subcat=T-Series&model=T3302
CPU: AMD Sempron™ 3300+ Processor (64-bit)
(2.0GHz, 1600MHz FSB, 256KB L2 cache)Operating System:
Genuine Microsoft® Windows® XP Home (SP2)
Chipset: VIA K8M800Memory: 512MB DDR SDRAM (1 × 512MB), 400MHz (PC3200)
Expandable to 2GBHard Drive: 160GB (7200rpm, 2MB cache)Optical Drive: 48x CD-RW/DVD Combo DriveMedia Reader: 8-in-1 digital media manager (Secure Digital™ (SD), Smart Media, Micro Drive, Memory Stick®, Memory Stick Pro®, Compact Flash, Mulitimedia Card, USB 2.0)Video: S3 Graphics Unichrome™ Pro
64MB DDR Shared memory
AGP 8x slot available for upgradeSound: AC '97 Audio, Dolby 5.1 (6-channel)Network: 10/100Mbps integrated Ethernet LANModem: 56K ITU V.92-ready Fax/ModemPeripherals: Standard Multifunction Keyboard, 2-Button Wheel Mouse, Amplified Stereo SpeakersPorts/Other: 5 USB 2.0 (4 in back, 1 in Media Reader), 1 VGA external connector, 1 serial, 1 parallel, 2 PS/2, 5 audio ports (2 in front, 3 in back)Dimensions: 14.25"H x 7.25"W x 16"DWeight: 22.5 lbs (PC only, no packaging)