I'm sorry to hear of your problems.
Now, it may be a hardware problem, so if you do feel 'comfortable', check as advised. However, you say the system has degraded over the period of a month...that doesn't indicate a hardware issue (they tend to just snap), aside from maybe a bad hard drive. But don't worry about that right now.
Let's try some simple things just to see if it is a software issue and if we can fix it
At the least, we can exclude some things. Now, to keep it simple, and I'm not going to charge you $xx..... please do the following:
Go to recovery console,
and do a checkdisk. To go to recovery console:
*Boot up from WinXP CD
*When the setup is loaded, press "r" to enter recovery console
*Press 1 for the setup number then hit ENTER
*Enter the Administrative passwordTo do a check disk:
*At the screen type this: "chkdsk X: /F" where "X" is your drive letter.
If you have 'any' problems in performing the instructions or encounter any problems, let me know. But hopefully, this should solve the problem allowing you to boot properly. If not, we'll ove on, but I will help you solve it.
Let me know how you get on