Yes, I have bought & used this program for more than a year on my Windows 98SE PC.
I don't think it does it's job too well & have not found a single of these so-called 'memory boosters' actually do the things they claim to do. I have 25-30 different programs like Memokit of which I've tried about 15. I now use Memokit to help me with certain tasks for which I didn't buy it in the first place!
Having said that I think you ought to try out some of them & see for yourself. There are a lot of shareware & freeware memory/system boosters that you can try & see what works best for your PC.
Please let me know & I'll send you the links to all of them, or, if that's too many the links to the 10 best ones (in my opinion, anyway).