Hi,
First off, you may find more help if you post to the "EOS DSLR & Mirrorless Cameras" forum: https://community.usa.canon.com/t5/EOS-DSLR-Mirrorless-Cameras/bd-p/eosdlsrandmirrorlesscameras
Second, the "Kiss X4", a.k.a. "Rebel T2i", a.k.a. "EOS 550D", was discontinued in June 2012, so I'm not too surprised that the software doesn't recognise it.
However, the camera uses SD cards for storage. You don't need any special software or drivers to access this; you just need an SD card reader attached to your computer. Take the SD card from the camera, plug it in to the reader, and just copy the files off using your computer's file browser. Remember to "safely remove" the SD card before unplugging it from your computer.
The manual says the camera is compatible with SD, SDHC, and SDXC memory cards. It doesn't say what capacities it can handle. You might need to stick with smaller cards for a camera that old.
If you shoot RAW, then you will need software which understands the Canon RAW format from that era. I don't have any camera that old to test with, but I would hope that most software which does RAW (e.g. RAW Therapee, etc.) would be OK. If you shoot JPEG, then you should have no issue: the files should be directly usable in any image viewer or editor.
BTW you can get the manual here, if you don't have it: https://www.canon.co.uk/support/consumer/products/cameras/eos/eos-550d.html?type=manuals
