The official Games for Windows site's posted recommended specs for the PC version of GTA IV, and looking at them, you may well have a computer able to handle it.
- OS: Windows XP SP2
- Processor: Dual core processor (Intel Pentium D or better)
- RAM: 2GB
- Hard Drive: 18GB free hard disk space
- Video Card: 512MB Direct3D 10 compatible video card or Direct3D 9 card compatible with Shader
- Drive: DVD-ROM dual-layer drive
The new version's out later this year.