My Dell Inspiron 9300 (Windows XP Home Edition + SP3) started playing up about 2 months ago. It takes about 3 minutes to get to the log-on screen then a further minute or so to a blue screen - no icons or task bar. The first few times it happened I got back to normal working using a restore point, but when I tried it again after not using it for a couple of weeks, the restore no longer solved the problem, even after trying a number of points well before the problem started. From the blue screen I can get Task Manager via ctrl-alt-del, and I can boot up in safe mode, with or without networking. I do not have (don't think I ever did have) a Windows XP boot/repair CD. Actions taken so far:
1. Set up new user profile
2. Removed all non windows related programs from start menu
3. Downloaded and ran malwarebytes. It found Adware Zango and two Trojans - Banker and Agent. It claims to have cleared these.
4. Ran Chkdsk /f /r. To my untutored eye nothing untoward, 0 KB in bad sectors.
5. Tried unsuccessfully to run sfc /scannow. In normal mode from Task Manager, Run, nothing happens. If I type cmd first then c:\windows\system32\sfc scannow at the prompt a Windows File Protection box opens, stating "please wait while Windows verifies that all protected Windows files are intact and in their original versions". Nothing happens and there is no evidence of any verifying going on. In Safe Mode I get message "the RPC Server is unavailable". In services.msc Remote Procedure Call is listed as started, but when I try to start RPC Locator I get "error 1084 - cannot be started in Safe Mode".
6. Re-ran malawarebytes, followed by Kaspersky full scan and TDSSKiller. All report clear.
7. Deleted all restore points. Don't know if this was sensible but was worried about possibility of reinfection.
I suppose there are corrupted files in the system caused by the Trojans but I don't feel competent to try any more sophisticated diagnostics/repair, except under expert supervision. Hope you can help!