Upgrading a Power Mac 7200.

Any video card you install must be one made for a Mac (or a PC card that has been flashed). It also has to be a PCI card. You are correct in you assessment of the HD- the internal drive is SCSI. Since the 7200 has PCI slots, you could add a PCI ATA card and use IDE drives. Small 50 pin SCSI drives (under 9 GB) are generally available at low prices on eBay.

Unless you just enjoy upgrading - and there's nothing wrong with that- you can quickly spend much more than the machine will ever be worth, so choose your upgrades carefully.

Here's a link to the specs for a 7200/120:
http://docs.info.apple.com/article.html?artnum=112357

For upgrading you also may look at:
http://www.whoopis.com/computerrepair/Power_Macintosh_7200Series.pdf

The ATI Radeon card's drivers require OS 9.2.1 or 9.2.2, which can only be installed on a 7200 that's running OS 9.1 and been updated to 9.2.1 or 9.2.2 using the third-party utility, "OS 9 Helper," and the downloadable OS 9.2.1 and 9.2.2 updates. There are older/less-expensive Mac video cards that will enable the use of VGA displays. The ATI XCLAIM Rage Pro (Mac) card comes with 4 MBs of SGRAM, with the option of an additional 4 MBs (plug-in SGRAM card). Many selling at eBay already have the 4 MB upgrade installed, and the card has both Mac and VGA ports. You can also use a Mac-to-VGA adapter, to convert the onboard monitor port for use of VGA displays. This assumes that the VRAM has been upgraded to at least 2 MBs (4 MBs is preferable).

In spite of having bought the 7200 for so little, I would discourage spending a lot of money to upgrade it. I bought a couple of 7200s in mint condition a few years ago. The 7200's power supply is compatible with the motherboard from a 7500, 7600, or 8500. I installed a pair of 8500 boards (including A/V modules) in mine, enabling the use of plug-in processor cards. With a 604e/233 MHz processor card and 1 MB L2 cache card, they were much faster than in their OEM configuration (601/75 MHz and 601/90 MHz). The amount of money I spent to boost their performance is ridiculous, given their negligible market value today. Whatever you do, don't buy one of Sonnet's 7200 G3 processor cards for a PCI slot. They've always been overpriced for what they are, and because so few were sold in comparison to the G3 (processor slot) upgrade cards, you won't find many bargain-priced 7200 PCI upgrades at eBay. In the end, the money spent on upgrading a 7200 could buy you a native beige G3 or B&W G3, both of which would easily outperform a G3-upgraded 7200. If you're upgrading your 7200 as a hobby project, choose upgrade cards that can be transferred to a newer Mac (video, ATA controller, USB and/or FireWire, etc.), because you'll never recover the money spent on them, if you were to sell the 7200 a day/week/month later.