The default page file on the Mini 9 with XP Home is set with a very small upper limit. If you only have an 8GB SSD
and 1GB RAM this is arguably a good thing. If you have anything else, it isn't too clever.
If you only have 512MB of RAM you are almost certainly going to need more than the default page fie size, and probably with 1GB also.
A basic rule of thumb is to set the maximum size at least the same as the size of your RAM, and to always set the minumum size equal to the maximum size (so XP expends no overhead continually adjusting its size). Normally being generous with the page file doesn't matter, but with the small SSDs in the Mini 9, you need to be more careful.
If you have 2GB of RAM you can disable the page file, which somewhat illogically will generally eliminate the low virtual memory message. This is because if there's a page file there, XP will tend to use it even if it doesn't need to, and if it isn't very large it will fill it and complain despite having lots of free RAM available (Linux and Vista handle this better). If the page file isn't there, XP can't try to use it, can't fill, it and it won't complain ... until you've filled all your 2GB of RAM, which actually takes some doing, at which point your system may crash.
For most people, 2GB of RAM is more than enough for XP on a Mini and a page file isn't needed, so unless the OP is running some extremely memory intensive tasks on their Mini, the page file should be disabled. If not comfortable with that, bump the min and max page file sizes up to at least 512MB.