I have a hp pavilion slimline s3700f with a nvidia geforce 6150 se graphics card and steam shows that oblivion requires

OS: Windows XP, Windows 2000, Windows XP 64-Bit
Processor: 2 Ghz Intel Pentium 4 or equivalent
Memory: 512 MB
Graphics: 128 MB Direct3D compatible video card and DirectX 9.0 compatible driver
DirectX®: DirectX 9.0c
Hard Drive: 4.6 GB
Sound: DirectX 8.1 compatible

I can't tell if it is compatible or not

Those are minimum requirements that you posted. Based on HP Pavilion Slimline s3700f Desktop PC- Product Specifications (http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01612604&cc=us&dlc=en&lc=en&jumpid=reg_R1002_USEN) and HP and Compaq Desktop PCs- Motherboard Specifications, M2N61-AR (Acacia) (http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01321559&tmp_track_link=ot_recdoc/c01612604/en_us/c01321559/loc:1&lc=en&dlc=en&cc=us), I would say yes it is compatable which isn't the same as awesomely playable. The recommended specs on my Oblivion box are 3 GHz. P4 Processor, 1 GB RAM, and a ATI X800 or NVIDIA 6800 series or higher video card. Don't be surprised if your 6150SE video is marginal or unsatisfactory.