Always check file hashes against a known Redump database. A legitimate XBLA ROM for Geometry Wars should be exactly 47.2 MB and contain a ContentCache.pkg file.
When the Xbox 360 launched in 2005, broadband internet was becoming standard, but digital storefronts were still novel. XBLA offered a curated selection of games that were easy to download, affordable ($5–$15), and often included demos. More importantly, it revived genres that AAA publishers had abandoned. Xbla Roms
Technical notes