Acer Aspire 5535 running vista.
Will booot up but instead of getting desktop screen I get black screen with bar across bottom and under that my start button and a few icons but when I try to click on these it says ' Windows explorer is not responding' and the little circle just keeps going around...
First see if you can start it in safe mode, and if you can from there you could try a system restore to an earlier date. I'm not familiar with Visa though. You could also run a few scans from there to check for viruses in case that is the problem.
How to boot into Safe Mode in Windows Vista
Restart the computer. Immediately after the screen goes blank for the first time, or after the BIOS post ends, start taping the F8 key repeatedly. The Windows Advanced Options menu appears. If the menu does not appear, restart the computer and try again. If the Keyboard has a [broken link removed], it may be necessary to press it first - QUICKLY before pressing the F8 Key. This will have to be done quickly before tapping the F8 key repeatedly.
The Windows Advanced Options Menu shown next should appear
The Safe Mode option uses a minimal set of device drivers and services to start Windows. The default Microsoft VGA driver is used for display at 640 x 480 or 800 x 600 resolution and in 16 colors.